- Correspondence to Dr Gregorio Barrio, Escuela Nacional de Sanidad, Instituto de Salud Carlos III, Madrid, Avda Monforte de Lemos, 5, Madrid 28029, Spain;
- Received October 10, 2014
- Revised March 2, 2015
- Accepted March 20, 2015
- First published April 13, 2015.
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