1. E.O.Hammerstad,Equations.for.microstrip.circuit.design,in.1975 Proceedings of 5th European Microwave Conference,pp.268-272.
2. C.M.Tsai,C.C.Tsai,and.S.Y.Lee,Nonsynchronous.alternating-impedance. transformers,in.2001 IEEE Proceedings of APMC,pp.310-313,Dec.2001.