University of KashanIranian Journal of Mathematical Chemistry2228-64896220151001Trigonometrically fitted two-step obrechkoff methods for the numerical solution of periodic initial value problems1451611045110.22052/ijmc.2015.10451ENA. ShokriDepartment of Mathematics, Faculty of Basic Science, University of Maragheh, Maragheh, Iran.A. A.ShokriDepartment of Mathematics, Ahar Branch, Islamic Azad University, Ahar, Iran.Sh. MostafaviFaculty of Mathematical Science, University of Maragheh, Maragheh, Iran.H. SaadatDepartment of Mathematics, Faculty of Basic Science, University of Maragheh, Maragheh, Iran20140518http://ijmc.kashanu.ac.ir/article_10451_e37900e24a74b6f240f6b1f76209f4e0.pdf