Submitted on: 27 January 1998.
Revised on: 08 April 1998.
Accepted on: 05 June 1998.
___________________Gaceta Sanitaria---ELSEVIER
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Submitted on: 18 June 2004.
Revised on: 09 October 2004.
Accepted on: 13 November 2004.
___________________Gaceta Sanitaria---ELSEVIER
Submitted on: 15 October 2022.
Revised on: 10 December 2022.
Accepted on: 05 February 2023.
___________________Gaceta Sanitaria---ELSEVIER
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