A discrete variational approach for investigation of stationary localized states in a discrete nonlinear Schrödinger equation, named IN-DNLS. Kundu, K. — 2005 International Journal of Mathematics and Mathematical Sciences
On symmetric derivatives and on properties of Zahorski N. K. Kundu — 1976 Czechoslovak Mathematical Journal
Symmetric derivative of nowhere monotone functions, I N. K. Kundu; S. N. Mukhopadhyay — 1970 Annales Polonici Mathematici