Angelo G Luvison - Academia.edu (original) (raw)

Papers by Angelo G Luvison

AEIT, 2012

Shannon ha trasformato l’“informazione” da una vaga idea in un concetto matematicamente definito.... more Shannon ha trasformato l’“informazione” da una vaga idea in un concetto matematicamente definito. L’articolo presenta una panoramica di applicazioni poco note, basate su metodi matematici e
computazionali della teoria dell’informazione, in mondi quali scommesse e azzardo, Borsa, giochi cooperativi

AEIT, 2016

Negli anni ’80 furono lanciati e realizzati programmi di cooperazione europea - quali ESPRIT e RA... more Negli anni ’80 furono lanciati e realizzati programmi di cooperazione europea - quali ESPRIT e RACE - per la ricerca precompetitiva nell’ informatica e nelle telecomunicazioni. L’articolo ricorda il contributo fornito da alcune di queste ricerche sia all’innovazione nell’ICT, sia all’effettiva evoluzione delle reti
broadband e ultrabroadband

AEIT, 2023

In un quadro complessivo di scarsa alfabetizzazione numerica, i giochi matematici possono fornire... more In un quadro complessivo di scarsa alfabetizzazione numerica, i giochi matematici possono fornire utili strumenti introduttivi al pensiero critico e al metodo scientifico per affrontare problemi di logica e probabilità quali si presentano quotidianamente in molteplici attività umane

AEIT, 2022

In un quadro di scarsa alfabetizzazione numerica, l’attenzione al bilancio energetico alimentare,... more In un quadro di scarsa alfabetizzazione numerica, l’attenzione al bilancio energetico alimentare, insieme alla qualità dei cibi e all’attività fisica, non è uno stravagante divertissement, ma rappresenta una responsabilità culturale, sociale ed economica per la salute e il benessere di ciascuno

CSELT Technical Reports, 1973

The paper considers the problem of the average error probability of linearly modulated digital sy... more The paper considers the problem of the average error probability of linearly modulated digital systems affeccted by intersymbol interfernce and Gaussian noise. The numerical averaging is based on high-precision quadrature and cubature rules and by starting from the moments of the involved statistical distribution.

AEIT, 2018

Comunicare in italiano su informatica, telecomunicazioni, tecnologie digitali in modo chiaro, acc... more Comunicare in italiano su informatica, telecomunicazioni, tecnologie digitali in modo chiaro, accurato, preciso e lessicalmente corretto può sembrare un obiettivo banale o futile, se non stravagante. Non è affatto così. Infatti, i tecnicismi settoriali aumentano di giorno in giorno e manca il tempo per assimilarne i dirompenti anglicismi

IEEE Transactions on Communications, 1973

Abstract-A new method is presented to compute the average prob-ability of error in the presence o... more Abstract-A new method is presented to compute the average prob-ability of error in the presence of intersymbol interference and additive noise for multilevel pule-amplitude-modulation (PAM) and partial-re-sponsecoded (PRO signaling schemes. The method is based upon ...

Optical Fiber Communications

This is the chapter "Topics in optical fibre communication theory" from the boo... more This is the chapter "Topics in optical fibre communication theory" from the book "Optical Fibre Communication" (1980) by Technical Staff of CSELT (Centro Studi e Laboratori Telecomunicazioni of Torino, Italy). It covers the most important system-theoretic research carried out at CSELT in the second half of 70s pertaining to both the analysis and design of optical fibre communication systems, e.g., generalization of the Poisson random process, direct detection, and digital systems. Even though time elapsed and optical technologies evolved since then, the theoretical and statistical approach adopted in this study should be considered methodologically valid still today.

IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. COM-32, NO. 6 , JUNE 1984

A unified method for approximating and bounding the average bit error probability for spread-spec... more A unified method for approximating and bounding the average bit error probability for spread-spectrum multiple-access communication systems is presented. Various forms of direct-sequence spread-spectrum modulation are considered including binary phase-shift keying, quadriphase-shift keying, and minimum-shift keying. The analysis of'the multiple-access interference makes use of a number of moments sufficent to evaluate the error probability with a high degree of accuracy. A computationally efficient algorithm for computing the moments i s also given. The subsequent transformation from the moments to the average bit error probability is carried out by means of Gauss-type numerical integration formulas. It is shown that the same approach can be exploited for evahating two classes of upper and lower bounds on the bit error rate. Finally, some results and comparisons are reported.

CSELT Rapporti Tecnici, 1973

The problem is considered of the average error probability of linearly-modulated digital systems ... more The problem is considered of the average error probability of linearly-modulated digital systems affected by intersymbol interference and Gaussian noise. First, the notation of complex envelope is used to represent the involved signals. Second, the average error probability is numerically computed by resorting to high-precision quadrature and cubature formulas for various PSK systems.
It is one of the first papers to compute in closed form the average error probability of linearly modulated digital systems affected by intersymbol interference and Gaussian noise. For the same problem in baseband digital systems, see: “Error probability in the presence of intersymbol interference and additive noise for multilevel digital signals”, IEEE Trans. Commun., vol. COM-21, March 1973, pp. 181-190,
For further advances in the application of numerical integration rules, see: 1) “Theoretical and experimental development of two-dimensional quadrature rules”, CSELT Rapporti Tecnici, vol. 5, Sept. 1977, pp. 245-249; and 2) “Moment-based performance evaluation of digital transmission systems”, IEE Proc.-I (Communications, Speech and Vision), vol. 139, June 1992, pp. 258-266.
This paper had already been presented at the "XX Congresso Internazionale delle Comunicazioni", Genova, Italy, Oct. 8-13, 1972, where it was awarded the prize for the best research work in telecommunications.

William R. Wells, Ed., Proc. 7th International Conference on Advances in Communications and Control (COMCON 7), 1999

Basic activities of the human society are education, work, leisure, entertainment and commerce. T... more Basic activities of the human society are education, work, leisure, entertainment and commerce. These terms are used here in a very broad sense, e.g. education may stand for academic or vocational training, commerce may be trading of both material and immaterial goods. The information society will be shaped by the modifications occurring in applications, services, systems and technologies that support these activities. The paper outlines major issues relating to the information society as well as to the associated Information and Communications Technology (ICT). It describes the major innovations in “networked” applications, where the attribute “networked” may imply different meanings, like “distance”, “tele”, “remote”, even “mobile” and “virtual”. The “networking effect” and new scenarios, knowledge and changing patterns of human activities, the need of systems thinking and awareness for ICT education are leitmotivs of the paper.

International Conference on Numerical Methods in Electrical and Magnetic Field Problems, 1976

A general algorithm for computing interpolatory two-dimensional quadrature formulas is described ... more A general algorithm for computing interpolatory two-dimensional quadrature formulas is described and tested. Particular emphasis is devoted to the presence of a weight function, which may be available in analytic form or not. Therefore, the algorithm assumes only the knowledge of the moments associated with the weight function. A discussion of some possible extensions and two practical examples related to engineering areas conclude the paper.

The Best of the Best: Fifty Years of Communications and Networking Research, 2007

A new method is presented to compute the average probability of error in the presence of inter... more A new method is presented to compute the average probability of error in the presence of intersymbol interference and additive noise for multilevel pule-amplitude-modulation (PAM). The method is based upon nonclassical Gauss quadrature rules (GQR) and suffers no limitation on noise statistics, so that it applies also for non-Gaussian noise. Moreover it yields some remarkable advantages as compared with other methods, in particular, with the series expansion method that has recently received considerable attention. Expressions for the truncation error are also given and their derivation is reported in the Appendix. Finally, examples of applications are presented and comparisons with other methods are carried out.

IEEE Transactions on Communications, 1984

A unified method for approximating and bounding the average bit error probability for spread-spec... more A unified method for approximating and bounding the average bit error probability for spread-spectrum multiple-access communication systems is presented. Various forms of direct-sequence spread- spectrum modulation are considered including binary phase-shift keying, quadriphase-shift keying, and minimum-shift keying. The analysis of'the multiple-access interference makes use of a number of moments sufficent to evaluate the error probability with a high degree of accuracy. A computationally efficient algorithm for computing the moments is also given. The subsequent transformation from the moments to the average bit error probability is carried out by means of Gauss-type numerical integration formulas. It is shown that the same approach can be exploited for evaluating two classes of upper and lower bounds on the bit error rate. Finally, some results and comparisons are reported.

Mondo Digitale – Rassegna critica del settore ICT, 2016

Da millenni, l'attività di intelligence è una funzione primaria delle agenzie governative dei più... more Da millenni, l'attività di intelligence è una funzione primaria delle agenzie governative dei più importanti Paesi. Ciò comporta l'impiego di sistemi di crittografia per la protezione di dati riservati, da un lato, e di crittanalisi per carpire tali informazioni, dall'altro. Più recentemente, la sicurezza informatica (cybersicurezza) è diventata un'esigenza di privati e di aziende, a cui si è opposto un incremento speculare dell'ingegno di malintenzionati nell'uso di tecniche crittografiche per fini disonesti, illeciti o illegali. L'articolo esplora alcuni aspetti del complesso problema privacy-sicurezza nel contesto del ruolo che la crittologia gioca in questi temi particolarmente caldi. Si introducono, in modo discorsivo e intuitivo, i principi di base dei sistemi a chiave pubblica, oltre a due recenti sviluppi in crittografia. Si accenna, infine, al cyber rischio dovuto al cosiddetto"fattore umano", se non adeguatamente governato.
From millennia, the issue of intelligence has been a major concern of government agencies in many countries. Therefore, cryptology techniques have been emerging in the dual role of cryptography to protect private information and cryptanalysis to get non-authorized access to the same information. In recent times, cybersecurity objectives, as extended to both personal and business sectors, witnessed a dramatic soaring of cybercrime activities, especially malware. The paper investigates a number of items in the intertwined relationship between privacy and security in the framework of the increasing role cryptology is expected to play in the future. The principles of public-key systems and other recent developments of cryptography are introduced in simple tutorial form. A final issue is how to contain the cyber risk stemming from "the human factor", when not properly controlled.

Working Document, 2019

This is a representative list of publications of Angelo Luvison on Information and Communications... more This is a representative list of publications of Angelo Luvison on Information and Communications Technology (ICT). The list covers research works spanning a period from the 70s to the present days. Broad study areas and timing are: 1) statistical communication theory (from 1970 to 1983); 2) analysis and design of networks and systems (from 1984 to 1999); 3) information society and social networks (from 2000); ICT ecosystem and critical decision making (from 2010). The paper topics and style have gradually moved from basic or applied research reporting (mainly in English) to popularization writing (in Italian).

Optical Fibre Communication, 1980

This is the chapter "Topics in optical fibre communication theory" from the book "Optical Fibre C... more This is the chapter "Topics in optical fibre communication theory" from the book "Optical Fibre Communication" (1980) by Technical Staff of CSELT (Centro Studi e Laboratori Telecomunicazioni of Torino, Italy). It covers the most important system-theoretic research carried out at CSELT in the second half of 70s pertaining to both the analysis and design of optical fibre communication systems, e.g., generalization of the Poisson random process, direct detection, and digital systems. Even though time elapsed and optical technologies evolved since then, the theoretical and statistical approach adopted in this study should be considered methodologically valid still today.

Trends in Optics and Photonics Vol. 20: Optical Networks and Their Applications, 1998

A report is given of FSAN (Full Services Access Networks), the international initiative that is a... more A report is given of FSAN (Full Services Access Networks), the international initiative that is aimed at streamlining the large-scale development of broadband optical access networks based on common specifications. FSAN is a joint effort of major world telecommunication operators and manufacturers. The paper explains the background of the FSAN activities, summarizes the organization and current directions of the work, and analyzes the operators' view showing areas of commonalty and difference. The FSAN agreement on architectures, functions, and interfaces is illustrated before the conclusion.

Electronics Letters, 1980

A simple numerical technique is proposed for the construction of the estimate of integrals which ... more A simple numerical technique is proposed for the construction of the estimate of integrals which represent the average error probability of many digital communication systems. Since these integrals are expressed as the expectation of some function of a random variable, their evaluation can be based on the knowledge of a number of moments of the variable. This is investigated from the viewpoint of discussing an algorithm based on interpolatory quadrature formulas which have equally spaced nodes. An example shows the satisfactory performance of the proposed approach.

AEIT, 2012

Shannon ha trasformato l’“informazione” da una vaga idea in un concetto matematicamente definito.... more Shannon ha trasformato l’“informazione” da una vaga idea in un concetto matematicamente definito. L’articolo presenta una panoramica di applicazioni poco note, basate su metodi matematici e
computazionali della teoria dell’informazione, in mondi quali scommesse e azzardo, Borsa, giochi cooperativi

AEIT, 2016

Negli anni ’80 furono lanciati e realizzati programmi di cooperazione europea - quali ESPRIT e RA... more Negli anni ’80 furono lanciati e realizzati programmi di cooperazione europea - quali ESPRIT e RACE - per la ricerca precompetitiva nell’ informatica e nelle telecomunicazioni. L’articolo ricorda il contributo fornito da alcune di queste ricerche sia all’innovazione nell’ICT, sia all’effettiva evoluzione delle reti
broadband e ultrabroadband

AEIT, 2023

In un quadro complessivo di scarsa alfabetizzazione numerica, i giochi matematici possono fornire... more In un quadro complessivo di scarsa alfabetizzazione numerica, i giochi matematici possono fornire utili strumenti introduttivi al pensiero critico e al metodo scientifico per affrontare problemi di logica e probabilità quali si presentano quotidianamente in molteplici attività umane

AEIT, 2022

In un quadro di scarsa alfabetizzazione numerica, l’attenzione al bilancio energetico alimentare,... more In un quadro di scarsa alfabetizzazione numerica, l’attenzione al bilancio energetico alimentare, insieme alla qualità dei cibi e all’attività fisica, non è uno stravagante divertissement, ma rappresenta una responsabilità culturale, sociale ed economica per la salute e il benessere di ciascuno

CSELT Technical Reports, 1973

The paper considers the problem of the average error probability of linearly modulated digital sy... more The paper considers the problem of the average error probability of linearly modulated digital systems affeccted by intersymbol interfernce and Gaussian noise. The numerical averaging is based on high-precision quadrature and cubature rules and by starting from the moments of the involved statistical distribution.

AEIT, 2018

Comunicare in italiano su informatica, telecomunicazioni, tecnologie digitali in modo chiaro, acc... more Comunicare in italiano su informatica, telecomunicazioni, tecnologie digitali in modo chiaro, accurato, preciso e lessicalmente corretto può sembrare un obiettivo banale o futile, se non stravagante. Non è affatto così. Infatti, i tecnicismi settoriali aumentano di giorno in giorno e manca il tempo per assimilarne i dirompenti anglicismi

IEEE Transactions on Communications, 1973

Abstract-A new method is presented to compute the average prob-ability of error in the presence o... more Abstract-A new method is presented to compute the average prob-ability of error in the presence of intersymbol interference and additive noise for multilevel pule-amplitude-modulation (PAM) and partial-re-sponsecoded (PRO signaling schemes. The method is based upon ...

Optical Fiber Communications

This is the chapter "Topics in optical fibre communication theory" from the boo... more This is the chapter "Topics in optical fibre communication theory" from the book "Optical Fibre Communication" (1980) by Technical Staff of CSELT (Centro Studi e Laboratori Telecomunicazioni of Torino, Italy). It covers the most important system-theoretic research carried out at CSELT in the second half of 70s pertaining to both the analysis and design of optical fibre communication systems, e.g., generalization of the Poisson random process, direct detection, and digital systems. Even though time elapsed and optical technologies evolved since then, the theoretical and statistical approach adopted in this study should be considered methodologically valid still today.

IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. COM-32, NO. 6 , JUNE 1984

A unified method for approximating and bounding the average bit error probability for spread-spec... more A unified method for approximating and bounding the average bit error probability for spread-spectrum multiple-access communication systems is presented. Various forms of direct-sequence spread-spectrum modulation are considered including binary phase-shift keying, quadriphase-shift keying, and minimum-shift keying. The analysis of'the multiple-access interference makes use of a number of moments sufficent to evaluate the error probability with a high degree of accuracy. A computationally efficient algorithm for computing the moments i s also given. The subsequent transformation from the moments to the average bit error probability is carried out by means of Gauss-type numerical integration formulas. It is shown that the same approach can be exploited for evahating two classes of upper and lower bounds on the bit error rate. Finally, some results and comparisons are reported.

CSELT Rapporti Tecnici, 1973

The problem is considered of the average error probability of linearly-modulated digital systems ... more The problem is considered of the average error probability of linearly-modulated digital systems affected by intersymbol interference and Gaussian noise. First, the notation of complex envelope is used to represent the involved signals. Second, the average error probability is numerically computed by resorting to high-precision quadrature and cubature formulas for various PSK systems.
It is one of the first papers to compute in closed form the average error probability of linearly modulated digital systems affected by intersymbol interference and Gaussian noise. For the same problem in baseband digital systems, see: “Error probability in the presence of intersymbol interference and additive noise for multilevel digital signals”, IEEE Trans. Commun., vol. COM-21, March 1973, pp. 181-190,
For further advances in the application of numerical integration rules, see: 1) “Theoretical and experimental development of two-dimensional quadrature rules”, CSELT Rapporti Tecnici, vol. 5, Sept. 1977, pp. 245-249; and 2) “Moment-based performance evaluation of digital transmission systems”, IEE Proc.-I (Communications, Speech and Vision), vol. 139, June 1992, pp. 258-266.
This paper had already been presented at the "XX Congresso Internazionale delle Comunicazioni", Genova, Italy, Oct. 8-13, 1972, where it was awarded the prize for the best research work in telecommunications.

William R. Wells, Ed., Proc. 7th International Conference on Advances in Communications and Control (COMCON 7), 1999

Basic activities of the human society are education, work, leisure, entertainment and commerce. T... more Basic activities of the human society are education, work, leisure, entertainment and commerce. These terms are used here in a very broad sense, e.g. education may stand for academic or vocational training, commerce may be trading of both material and immaterial goods. The information society will be shaped by the modifications occurring in applications, services, systems and technologies that support these activities. The paper outlines major issues relating to the information society as well as to the associated Information and Communications Technology (ICT). It describes the major innovations in “networked” applications, where the attribute “networked” may imply different meanings, like “distance”, “tele”, “remote”, even “mobile” and “virtual”. The “networking effect” and new scenarios, knowledge and changing patterns of human activities, the need of systems thinking and awareness for ICT education are leitmotivs of the paper.

International Conference on Numerical Methods in Electrical and Magnetic Field Problems, 1976

A general algorithm for computing interpolatory two-dimensional quadrature formulas is described ... more A general algorithm for computing interpolatory two-dimensional quadrature formulas is described and tested. Particular emphasis is devoted to the presence of a weight function, which may be available in analytic form or not. Therefore, the algorithm assumes only the knowledge of the moments associated with the weight function. A discussion of some possible extensions and two practical examples related to engineering areas conclude the paper.

The Best of the Best: Fifty Years of Communications and Networking Research, 2007

A new method is presented to compute the average probability of error in the presence of inter... more A new method is presented to compute the average probability of error in the presence of intersymbol interference and additive noise for multilevel pule-amplitude-modulation (PAM). The method is based upon nonclassical Gauss quadrature rules (GQR) and suffers no limitation on noise statistics, so that it applies also for non-Gaussian noise. Moreover it yields some remarkable advantages as compared with other methods, in particular, with the series expansion method that has recently received considerable attention. Expressions for the truncation error are also given and their derivation is reported in the Appendix. Finally, examples of applications are presented and comparisons with other methods are carried out.

IEEE Transactions on Communications, 1984

A unified method for approximating and bounding the average bit error probability for spread-spec... more A unified method for approximating and bounding the average bit error probability for spread-spectrum multiple-access communication systems is presented. Various forms of direct-sequence spread- spectrum modulation are considered including binary phase-shift keying, quadriphase-shift keying, and minimum-shift keying. The analysis of'the multiple-access interference makes use of a number of moments sufficent to evaluate the error probability with a high degree of accuracy. A computationally efficient algorithm for computing the moments is also given. The subsequent transformation from the moments to the average bit error probability is carried out by means of Gauss-type numerical integration formulas. It is shown that the same approach can be exploited for evaluating two classes of upper and lower bounds on the bit error rate. Finally, some results and comparisons are reported.

Mondo Digitale – Rassegna critica del settore ICT, 2016

Da millenni, l'attività di intelligence è una funzione primaria delle agenzie governative dei più... more Da millenni, l'attività di intelligence è una funzione primaria delle agenzie governative dei più importanti Paesi. Ciò comporta l'impiego di sistemi di crittografia per la protezione di dati riservati, da un lato, e di crittanalisi per carpire tali informazioni, dall'altro. Più recentemente, la sicurezza informatica (cybersicurezza) è diventata un'esigenza di privati e di aziende, a cui si è opposto un incremento speculare dell'ingegno di malintenzionati nell'uso di tecniche crittografiche per fini disonesti, illeciti o illegali. L'articolo esplora alcuni aspetti del complesso problema privacy-sicurezza nel contesto del ruolo che la crittologia gioca in questi temi particolarmente caldi. Si introducono, in modo discorsivo e intuitivo, i principi di base dei sistemi a chiave pubblica, oltre a due recenti sviluppi in crittografia. Si accenna, infine, al cyber rischio dovuto al cosiddetto"fattore umano", se non adeguatamente governato.
From millennia, the issue of intelligence has been a major concern of government agencies in many countries. Therefore, cryptology techniques have been emerging in the dual role of cryptography to protect private information and cryptanalysis to get non-authorized access to the same information. In recent times, cybersecurity objectives, as extended to both personal and business sectors, witnessed a dramatic soaring of cybercrime activities, especially malware. The paper investigates a number of items in the intertwined relationship between privacy and security in the framework of the increasing role cryptology is expected to play in the future. The principles of public-key systems and other recent developments of cryptography are introduced in simple tutorial form. A final issue is how to contain the cyber risk stemming from "the human factor", when not properly controlled.

Working Document, 2019

This is a representative list of publications of Angelo Luvison on Information and Communications... more This is a representative list of publications of Angelo Luvison on Information and Communications Technology (ICT). The list covers research works spanning a period from the 70s to the present days. Broad study areas and timing are: 1) statistical communication theory (from 1970 to 1983); 2) analysis and design of networks and systems (from 1984 to 1999); 3) information society and social networks (from 2000); ICT ecosystem and critical decision making (from 2010). The paper topics and style have gradually moved from basic or applied research reporting (mainly in English) to popularization writing (in Italian).

Optical Fibre Communication, 1980

This is the chapter "Topics in optical fibre communication theory" from the book "Optical Fibre C... more This is the chapter "Topics in optical fibre communication theory" from the book "Optical Fibre Communication" (1980) by Technical Staff of CSELT (Centro Studi e Laboratori Telecomunicazioni of Torino, Italy). It covers the most important system-theoretic research carried out at CSELT in the second half of 70s pertaining to both the analysis and design of optical fibre communication systems, e.g., generalization of the Poisson random process, direct detection, and digital systems. Even though time elapsed and optical technologies evolved since then, the theoretical and statistical approach adopted in this study should be considered methodologically valid still today.

Trends in Optics and Photonics Vol. 20: Optical Networks and Their Applications, 1998

A report is given of FSAN (Full Services Access Networks), the international initiative that is a... more A report is given of FSAN (Full Services Access Networks), the international initiative that is aimed at streamlining the large-scale development of broadband optical access networks based on common specifications. FSAN is a joint effort of major world telecommunication operators and manufacturers. The paper explains the background of the FSAN activities, summarizes the organization and current directions of the work, and analyzes the operators' view showing areas of commonalty and difference. The FSAN agreement on architectures, functions, and interfaces is illustrated before the conclusion.

Electronics Letters, 1980

A simple numerical technique is proposed for the construction of the estimate of integrals which ... more A simple numerical technique is proposed for the construction of the estimate of integrals which represent the average error probability of many digital communication systems. Since these integrals are expressed as the expectation of some function of a random variable, their evaluation can be based on the knowledge of a number of moments of the variable. This is investigated from the viewpoint of discussing an algorithm based on interpolatory quadrature formulas which have equally spaced nodes. An example shows the satisfactory performance of the proposed approach.

Opticl Fibre Communication, 1980

This is the chapter "Topics in optical fibre communication theory" from the book "Optical Fibre C... more This is the chapter "Topics in optical fibre communication theory" from the book "Optical Fibre Communication" (1980) by Technical Staff of CSELT (Centro Studi e Laboratori Telecomunicazioni of Torino, Italy). It covers the most important system-theoretic research carried out at CSELT in the second half of 70s pertaining to both the analysis and design of optical fibre communication systems, e.g., generalization of the Poisson random process, direct detection, and digital systems. Even though time elapsed and optical technologies evolved since then, the theoretical and statistical approach adopted in this study should be considered methodologically valid still today.