A block lower triangular preconditioner for a class of complex symmetric   system of linear equations
  We present a block lower triangular (BLT) preconditioner to accelerate the convergence of nthe Krylov subspace iterative methods, such as generalized minimal residual (GMRES), for solving a broad class of complex symmetric system of linear equations. We analyze the eigenvalues distribution of preconditioned coefficient matrix. Numerical experiments are given to demonstrate the effectiveness of the BLT preconditioner. 
Davod Khojasteh Salkuyeh and Tahereh Salimi Siahkalaei
math.NA