Submitted on: 28 March 2006.
Revised on: 12 June 2006.
Accepted on: 23 June 2006.
___________________Bulletin of the Iranian Mathematical Society
Submitted on: 07 November 2001.
Revised on: 14 January 2002.
Accepted on: 04 February 2002.
___________________Bulletin of the Iranian Mathematical Society
http://reply.papertrans.cn/1/44/4374/4374-33.png
Submitted on: 09 July 2011.
Revised on: 19 October 2011.
Accepted on: 11 December 2011.
___________________Bulletin of the Iranian Mathematical Society
Submitted on: 19 December 2009.
Revised on: 11 March 2010.
Accepted on: 01 April 2010.
___________________Bulletin of the Iranian Mathematical Society
Submitted on: 25 March 2004.
Revised on: 12 July 2004.
Accepted on: 30 August 2004.
___________________Bulletin of the Iranian Mathematical Society