1. Lathi, B.P.: Modern digital and analog communication systems, (Holt-Saunders 1983),Chap. 4, p. 294
2. Carlson, A.B.: Communication systems, 2nd edn(McGraw-Hill 1975),Chap. 6, p. 236
3. Taub, H., and Schilling, D.L.: Principles of communication systems, 2nd edn(McGraw-Hill 1986),Chap. 4, p. 153