Sivaramakrishnan Ramakrishna Ayyar has served a few educational institutions in Kerala as a math-teacher. In particular, he has served the university of Calicut, Kerala-673635 during the years 1977-1996. A monograph entitled: ‘Classical Theory of Arithmetic Functions’ (Marcel Dekker (1989)) was published during his visitorship (1987-88) at the University of Kansas, Lawrence, KS66045, U.S.A. He has also visited Mangalore University (1996-1997), Mangalagangotri, Mangalore-574199. He holds an Emeritus membership of American Mathematical Society, since 2008. His e-mail address is: rsjreeg@gmail.com. The first edition of this book was published in the year 2006 (Chapman & Hall/CRC (Tayor & Francis Group)) when he could receive a Government of India Grant under ‘Utilization of Services of Retired Scientists’ (USERS) scheme to work at the University of Calicut during the two-year period April, 2000–March, 2002.