Submitted on: 12 March 2008.
Revised on: 19 March 2008.
Accepted on: 30 March 2008.
REVUE ECONOMIQUE---PRESSES FOND NAT SCI POLIT
Submitted on: 07 November 2017.
Revised on: 02 December 2017.
Accepted on: 25 December 2017.
NULL
Submitted on: 27 January 2020.
Revised on: 07 March 2020.
Accepted on: 22 March 2020.
NULL
http://reply.papertrans.cn/3/272/27159/27159-34.png
http://reply.papertrans.cn/3/272/27159/27159-35.png
http://reply.papertrans.cn/3/272/27159/27159-36.png