Periodic wave solutions of nonlinear equations by Hirota's bilinear   method
  In this paper, we use Hirota's bilinear method to directly construct periodic wave solutions of nonlinear equations.   The asymptotic property of periodic wave solutions are analyzed. It is shown that well-known soliton solutions can be reduced from the periodic wave solutions. 
H.H. Dai, E. G. Fan X. G. Geng