[1] K. M. Chen, V. Liepa, IEEE Trans. on AP, AP-12(1964), 576-582.[2]K. M. Chen, IEEE Trans. on AP, AP-14(1966), 318-323.[3]K. M. Chen, IEEE Trans. on AP, AP-13(1965), 263-270.[4]I. P. Yu, L. C. Shen, IEEE Trans. on AP, AP-19(1971), 554-557.[5]W. L. Stutzman, G. A. Thiele, Antenna Theory and Design, Wiley, New York, (1981), p. 331.[6]K. F. Lee.[J].Principle of Antenna Theary, JohnwHeySons.1984,:-