Hola Fernando,
Easy!
Just looked in Forton's Navajas Antiguas/Las Mejores Piezas de Coleccion - Well worth getting if one is into navajas.
Another new book that may interest you is the one recently written by Abel Domenech: Dagas de Plata. It is the definitive work on Gaucho knives. You can find him on the internet. A friend showed me a copy and I was blown away. Unfortunatley for English readers, for the time being, it is only available in Spanish.
Saludos
Chris