In this paper, we extend the hyperbolic function approach for constructing the exact solutions of nonlinear differential-difference equation (NDDE) in a unified
Based on the vector graviton metric theory of gravitation (VGM) suggested by one of the authors of this article, using the method of null tetrad and analytic co
The interaction of N two-level atoms with both a two-mode cavity field and an external classical pumpingfield, and with the fields being degenerate in frequency