Submitted on: 30 March 1999.
Revised on: 10 May 1999.
Accepted on: 19 May 1999.
Turkish Journal of Mathematics
http://reply.papertrans.cn/4/301/30062/30062-32.png
http://reply.papertrans.cn/4/301/30062/30062-33.png
Submitted on: 13 April 2008.
Revised on: 16 May 2008.
Accepted on: 10 June 2008.
Turkish Journal of Mathematics
Submitted on: 30 June 2015.
Revised on: 30 July 2015.
Accepted on: 19 August 2015.
Turkish Journal of Mathematics
Submitted on: 25 August 2014.
Revised on: 05 September 2014.
Accepted on: 30 September 2014.
Turkish Journal of Mathematics