- Correspondence to Professor Marc Saez, Research Group on Statistics, Econometrics and Health (GRECS), CIBER of Epidemiology and Public Health (CIBERESP), University of Girona, Campus de Montilivi, Girona 17071, Spain;
- Received March 18, 2013
- Revised May 8, 2013
- Accepted May 27, 2013
- First published June 22, 2013.
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