Submitted on: 26 June 1999.
Revised on: 27 July 1999.
Accepted on: 18 August 1999.
NULL
http://reply.papertrans.cn/3/265/26403/26403-12.png
Submitted on: 21 March 2016.
Revised on: 01 May 2016.
Accepted on: 17 May 2016.
NULL
http://reply.papertrans.cn/3/265/26403/26403-14.png
http://reply.papertrans.cn/3/265/26403/26403-15.png
Submitted on: 12 December 2010.
Revised on: 02 January 2011.
Accepted on: 25 January 2011.
NULL
Submitted on: 11 April 2017.
Revised on: 06 May 2017.
Accepted on: 26 May 2017.
Research in Economics---ELSEVIER SCI LTD
http://reply.papertrans.cn/3/265/26403/26403-18.png
http://reply.papertrans.cn/3/265/26403/26403-19.png
http://reply.papertrans.cn/3/265/26403/26403-20.png