[Pidstryhach Inst. Appl. Problems of Mech. & Math.. NASU 6th International Seminar/Workshop Direct and Inverse Problems of Electromagnetic and Acoustic Wave Theory. DIPED-2001 - Lviv, Ukraine (18-20 Sept. 2001)] DIPED - 2001. Proceedings of 6th International Seminar/Workshop on Direct and Inverse Problems of Electromagnetic and Acoustic Wave Theory (IEEE Cat. No.01TH8554) - Effective method to solve the diffraction on periodical surface problems