W. D. Wallis is Professor of Mathematics at Southern Illinois University at Carbondale. The author of Combinatorial Designs (Marcel Dekker, Inc.), he is a member of the American Mathematical Society, Mathematical Association of America, Australian Mathematical Society, and Combinatorial Mathematics Society of Australia. Dr. Wallis received the B.Sc. (1963) and Ph.D. (1968) degrees in mathematics from the University of Sydney, Australia. H. Shen is an Associate Professor in the Department of Applied Mathematics at Shanghai Jiao Tbng University, Shanghai, People’s Republic of China. A member of the Standing Committee of the Combinatorics Society of China, Professor Shen received the M.Sc. degree (1982) from Shanghai Jiao Tbng University. W. Wei is a Professor in the Department of Mathematics at Sichuan University, Chengdu, People’s Republic of China. Deputy President of the Combinatorics Society of China and a member of the American Mathematical Society and Committee of Combinatorics and Graph Theory of the Chinese Mathematical Society, Professor Wei graduated (1961) from Sichuan University. L. Zhu is a Professor in the Department of Mathematics at Suzhou University, Suzhou, People’s Republic of China. A member of the Chinese Mathematical Society and the Standing Committee of the Combinatorics Society of China, Professor Zhu studied at Jiangsu Tfeachers College from 1961-1965. Less