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Submitted on: 17 August 1999.
Revised on: 11 November 1999.
Accepted on: 09 December 1999.
___________________Journal of Adolescent Health---ELSEVIER SCIENCE INC
Submitted on: 18 April 2003.
Revised on: 24 July 2003.
Accepted on: 11 September 2003.
___________________Journal of Adolescent Health---ELSEVIER SCIENCE INC
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