Minimality on biharmonic space-like submanifolds in pseudo-Riemannian space forms

In this paper, we investigate the minimality or the constraint of the mean curvature of three kinds of biharmonic space-like submanifolds in pseudo-Riemannian space forms: (1) pseudo-umbilical ones; (2) the ones with parallel mean curvature vector; (3) with constant mean curvature.