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Submitted on: 22 September 1998.
Revised on: 17 October 1998.
Accepted on: 02 November 1998.
___________________JOURNAL OF NETWORK AND COMPUTER APPLICATIONS
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Submitted on: 06 May 2007.
Revised on: 09 June 2007.
Accepted on: 29 July 2007.
___________________JOURNAL OF NETWORK AND COMPUTER APPLICATIONS
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