Sansone G. Orthogonal Functions

N.-Y.: Dover, 1991. - 180p.The theory of orthogonal expansions had its origin in the debate concerning the vibrating string which animated the mathematical world two hundred years ago. It has since become an important area of modern mathematical thought. This highly regarded treatise presents the classical theory of orthogonal series with rigorous attention to detail and appropriate technique, but in an easy-to-read style. The book contains a wealth of information, factual and bibliographical, that will prove especially valuable to the applied mathematician who very often does not have access to original papers. He will find here a rich compilation of general results and convenient criteria concerning Fourier series, Legendre series, Laguerre and Hermite polynomials.