Synopsis: Many theoretical and applied questions of mathematical physics, mechanics and other sciences form spectral problems for operator-valued functions that linearly or nonlinearly depend on two or more parameters, so-called two-parameter or multiparameter spectral problems. In this book the two approaches to the variational formulation of problems of solving both linear and nonlinear multiparameter spectral problems are proposed. There are presented and proved the algorithms for their solution. For two-parameter problems,...