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Submitted on: 10 March 2000.
Revised on: 02 July 2000.
Accepted on: 06 August 2000.
___________________Chronica Nova---UNIV GRANADA
Submitted on: 11 April 1998.
Revised on: 12 May 1998.
Accepted on: 17 June 1998.
___________________Chronica Nova---UNIV GRANADA
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