- Correspondence to Dr M Adrian Ortega-Guerrero, Universidad Nacional Autónoma de México, Centro de Geociencias, Campus Juriquilla, Boulevard Juriquilla 3001, Querétaro, PC 76230, Mexico;
- Received October 31, 2013
- Revised August 11, 2014
- Accepted September 1, 2014
- First published September 17, 2014.
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