Submitted on: 26 October 2011.
Revised on: 07 December 2011.
Accepted on: 31 January 2012.
___________________Forum of Mathematics Pi---CAMBRIDGE UNIV PRESS
http://reply.papertrans.cn/2/101/10067/10067-12.png
Submitted on: 17 August 2011.
Revised on: 29 October 2011.
Accepted on: 20 November 2011.
___________________Forum of Mathematics Pi---CAMBRIDGE UNIV PRESS
http://reply.papertrans.cn/2/101/10067/10067-14.png
http://reply.papertrans.cn/2/101/10067/10067-15.png
Submitted on: 04 May 2001.
Revised on: 17 July 2001.
Accepted on: 05 September 2001.
___________________Forum of Mathematics Pi---CAMBRIDGE UNIV PRESS
http://reply.papertrans.cn/2/101/10067/10067-17.png
Submitted on: 23 October 1999.
Revised on: 16 January 2000.
Accepted on: 23 February 2000.
___________________Forum of Mathematics Pi---CAMBRIDGE UNIV PRESS
http://reply.papertrans.cn/2/101/10067/10067-19.png
http://reply.papertrans.cn/2/101/10067/10067-20.png