- Correspondence to María Fernanda Martínez-Salazar, Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, CP 11350 Ciudad de México, México;
- Received 15 September 2016
- Revised 4 January 2017
- Accepted 16 January 2017
- Published online 16 March 2017.
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