http://reply.papertrans.cn/2/136/13583/13583-11.png
http://reply.papertrans.cn/2/136/13583/13583-12.png
http://reply.papertrans.cn/2/136/13583/13583-13.png
http://reply.papertrans.cn/2/136/13583/13583-14.png
http://reply.papertrans.cn/2/136/13583/13583-15.png
Submitted on: 24 May 2003.
Revised on: 20 July 2003.
Accepted on: 10 September 2003.
___________________INTERNATIONAL JOURNAL OF INDUSTRIAL ORGANIZATION
Submitted on: 26 April 2008.
Revised on: 07 June 2008.
Accepted on: 04 August 2008.
___________________INTERNATIONAL JOURNAL OF INDUSTRIAL ORGANIZATION
http://reply.papertrans.cn/2/136/13583/13583-18.png
Submitted on: 14 October 2001.
Revised on: 17 November 2001.
Accepted on: 05 December 2001.
___________________INTERNATIONAL JOURNAL OF INDUSTRIAL ORGANIZATION
Submitted on: 20 November 2013.
Revised on: 03 March 2014.
Accepted on: 20 March 2014.
___________________INTERNATIONAL JOURNAL OF INDUSTRIAL ORGANIZATION