- Correspondence to Dr Lourdes García-García, Instituto Nacional de Salud Pública, Av. Universidad # 655, Col. Sta. María Ahuacatitlán, Cuernavaca, Morelos C.P. 62100, México;
- Received February 29, 2012
- Revised October 15, 2012
- Accepted November 24, 2012
- First published December 18, 2012.
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