Becerra, C H
Contreras-García, G A
Perez Vera, L A
Díaz-Martínez, L A
Beltran Avendaño, M A
Salazar Martínez, H A
Article History
Received: 9 December 2013
Revised: 30 June 2014
Accepted: 7 July 2014
First Online: 25 November 2014
Competing interests
: The authors declare no conflict of interest.