. 2001 Jul 31;2:7. doi: 10.1186/1471-2172-2-7
Copyright © 2001 Domínguez-Gerpe and Rey-Méndez; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL.