1. Interpolation problems play an important role both in theoretical and applied investigations. This explains the great number of works dedicated to classical and new interpolation problems ( 1)- 5], 8), 13)- 16], 26)- 30], 57]). In this book we use a method of operator identities for investigating interpo- lation problems. Following the method of operator identities we formulate a general interpolation problem containing the classical interpolation...