The center conditions and bifurcation of limit cycles for a class of fifth degree systems are investigated. Two recursive formulas to compute singular quantitie
A new discrete isospectral problem is introduced, from which a hierarchy of Laxintegrable lattice equation is deduced. By using the trace identity, the correspo
In this paper,some existence results for the fourth order nonlinear subelliptic equations on the Hesisenberg group are given by means of varational methods.