High phase-lag order trigonometrically fitted two-step Obrechkoff   methods for the numerical solution of periodic initial value problems
  In this paper, we present the two-step trigonometrically fitted symmetric Obrechkoff methods with algebraic order of twelve. The method is based on the symmetric two-step Obrechkoff method, with 12 algebraic order, high phase-lag order and is constructed to solve IVPs with periodic solutions such as orbital problems. We compare the new method to some recently constructed optimized methods from the literature. The numerical results obtained by the new method for some problems show its superiority in efficiency, accuracy and stability. 
Ali Shokri, Hosein Saadat
math.NA