Submitted on: 03 November 2001.
Revised on: 20 November 2001.
Accepted on: 12 December 2001.
Milan Journal of Mathematics---SPRINGER BASEL AG
Submitted on: 24 September 2016.
Revised on: 28 October 2016.
Accepted on: 03 November 2016.
Milan Journal of Mathematics
http://reply.papertrans.cn/3/220/21998/21998-13.png
Submitted on: 24 February 2005.
Revised on: 11 March 2005.
Accepted on: 22 March 2005.
Milan Journal of Mathematics---SPRINGER BASEL AG
http://reply.papertrans.cn/3/220/21998/21998-15.png
http://reply.papertrans.cn/3/220/21998/21998-16.png
Submitted on: 21 December 1999.
Revised on: 02 January 2000.
Accepted on: 17 January 2000.
Milan Journal of Mathematics
Submitted on: 13 August 2002.
Revised on: 29 August 2002.
Accepted on: 11 September 2002.
Milan Journal of Mathematics
http://reply.papertrans.cn/3/220/21998/21998-19.png
Submitted on: 13 May 2020.
Revised on: 11 June 2020.
Accepted on: 25 June 2020.
Milan Journal of Mathematics