CIBERGRAFÍA.

http://www.cundinamarca.gov.co/cundinamarca/archivos/FILE_EVENTOSENTI/FILE_EVENTOSENTI10332.pdf

http://www.ceba.com.co/index.php?option=com_virtuemart&page=shop.browse&category_id=118&Itemid=6&vmcchk=1&Itemid=6

http://www.mylagro.com/categories/Semillas/Pastos-y-Forraje/Clima-frio/

http://www.linkagro.com/component/content/article/34-importadora-alaska/338-semillas-de-leguminosas-de-clima-frio-trebol

https://www.youtube.com/watch?v=VXE_Gp-x5Fo&feature=player_detailpage