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Submitted on: 22 December 2002.
Revised on: 15 March 2003.
Accepted on: 26 March 2003.
___________________ANNALES DE BRETAGNE ET DES PAYS DE L OUEST
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http://reply.papertrans.cn/1/17/1691/1691-34.png
Submitted on: 28 May 2013.
Revised on: 01 July 2013.
Accepted on: 07 August 2013.
___________________ANNALES DE BRETAGNE ET DES PAYS DE L OUEST
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