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Submitted on: 15 January 2010.
Revised on: 18 February 2010.
Accepted on: 11 March 2010.
NULL
Submitted on: 15 October 2006.
Revised on: 03 November 2006.
Accepted on: 15 November 2006.
Research in Economics---ELSEVIER SCI LTD
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Submitted on: 27 June 2021.
Revised on: 09 July 2021.
Accepted on: 27 July 2021.
Research in Economics---ELSEVIER SCI LTD
http://reply.papertrans.cn/3/265/26403/26403-27.png
Submitted on: 31 August 2021.
Revised on: 30 September 2021.
Accepted on: 13 October 2021.
Research in Economics---ELSEVIER SCI LTD
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