http://reply.papertrans.cn/2/185/18455/18455-31.png
http://reply.papertrans.cn/2/185/18455/18455-32.png
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http://reply.papertrans.cn/2/185/18455/18455-35.png
Submitted on: 13 August 1999.
Revised on: 21 October 1999.
Accepted on: 19 November 1999.
___________________JOURNAL OF OPERATIONS MANAGEMENT