Submitted on: 12 March 2006.
Revised on: 16 April 2006.
Accepted on: 04 May 2006.
___________________Empirical Economics---PHYSICA-VERLAG GMBH & CO
Submitted on: 05 July 2006.
Revised on: 13 August 2006.
Accepted on: 12 October 2006.
___________________Empirical Economics---PHYSICA-VERLAG GMBH & CO
http://reply.papertrans.cn/1/84/8318/8318-33.png
http://reply.papertrans.cn/1/84/8318/8318-34.png
Submitted on: 22 February 2000.
Revised on: 11 April 2000.
Accepted on: 02 June 2000.
___________________Empirical Economics---PHYSICA-VERLAG GMBH & CO
http://reply.papertrans.cn/1/84/8318/8318-36.png