Cavalli-Sforza, Luca (julio de 1997). «Genes, peoples, and languages». Proceedings of the National Academy of Sciences of the United States of America94 (15): 7719-7724. Consultado el 28 de julio de 2009. «Hidden patterns in the geography of Europe shown by the first five principal components, explaining respectively 28%, 22%, 11%, 7%, and 5% of the total genetic variation for 95 classical polymorphisms (1, 13, 14).»
