Sufficient conditions for functions to form Riesz bases in L 2 and applications to nonlinear boundary-value problems. Zhidkov, Peter E. — 2001 Electronic Journal of Differential Equations (EJDE) [electronic only]
On an infinite sequence of invariant measures for the cubic nonlinear Schrödinger equation. Zhidkov, Peter E. — 2001 International Journal of Mathematics and Mathematical Sciences