http://www.wmo.int/pages/prog/wcp/ccl/guide/documents/wmo_100_es.pdf
http://www.whycos.org/hwrp/guide/index_es.php
http://www.wmo.int/pages/prog/wcp/agm/gamp/gamp_en.php
http://eca.knmi.nl/documents/WCDMP_72_TD_1500_en_1.pdf