http://reply.papertrans.cn/1/4/369/369-11.png
Submitted on: 08 September 2003.
Revised on: 25 December 2003.
Accepted on: 04 February 2004.
___________________Acta Mathematica Vietnamica---SPRINGER SINGAPORE PTE LTD
Submitted on: 19 January 1999.
Revised on: 28 March 1999.
Accepted on: 10 April 1999.
___________________Acta Mathematica Vietnamica---SPRINGER SINGAPORE PTE LTD
Submitted on: 01 January 2003.
Revised on: 25 March 2003.
Accepted on: 08 April 2003.
___________________Acta Mathematica Vietnamica---SPRINGER SINGAPORE PTE LTD
http://reply.papertrans.cn/1/4/369/369-15.png
Submitted on: 11 January 1999.
Revised on: 14 February 1999.
Accepted on: 01 April 1999.
___________________Acta Mathematica Vietnamica---SPRINGER SINGAPORE PTE LTD
Submitted on: 14 December 2021.
Revised on: 16 February 2022.
Accepted on: 02 March 2022.
___________________Acta Mathematica Vietnamica---SPRINGER SINGAPORE PTE LTD
http://reply.papertrans.cn/1/4/369/369-18.png
http://reply.papertrans.cn/1/4/369/369-19.png
Submitted on: 29 September 1998.
Revised on: 23 December 1998.
Accepted on: 23 January 1999.
___________________Acta Mathematica Vietnamica---SPRINGER SINGAPORE PTE LTD