http://reply.papertrans.cn/2/152/15197/15197-31.png
http://reply.papertrans.cn/2/152/15197/15197-32.png
Submitted on: 04 November 1999.
Revised on: 18 December 1999.
Accepted on: 11 January 2000.
___________________JOURNAL OF ALGEBRAIC COMBINATORICS
http://reply.papertrans.cn/2/152/15197/15197-34.png
http://reply.papertrans.cn/2/152/15197/15197-35.png
http://reply.papertrans.cn/2/152/15197/15197-36.png