A couple of links didn't work. I share them all fixed below. Factorigami, by Leonardo Pulido Martínez (math booklet in Spanish)
A Basket for Grettell, by Javier Domínguez Pérez -- Gerardo G. gerardo(a)neorigami.com instagram.com/neorigamicomKnowledge and Curiosity in Origami: six private classes online "(...) It doesn’t happen often, but when it does, it takes your breath away and fills you with the true joy of origami. I experienced this in my lessons with Gerardo G. I wouldn’t trade it for anything. Gerardo is (...)" C. R. Read the full review