@inbook {1997, title = {Functionals of the Peierls - Fr{\"o}hlich Type and the Variational Principle for the Whitham Equations}, booktitle = {Solitons, geometry, and topology : on the crossroad / V. M. Buchstaber, S. P. Novikov editors.- Providence : American Mathematical Society, 1997. - ( American mathematical society translations. Series 2. - vol. 179). - pages : 35-44}, number = {American mathematical society translations. Series 2.;v.179}, year = {1997}, publisher = {American Mathematical Society}, organization = {American Mathematical Society}, isbn = {0821806661}, url = {http://hdl.handle.net/1963/6485}, author = {Boris Dubrovin} }