There is a another very extensive study of Nahuatl riddles " 'Tan ancha como tu abuela': Adivinanzas en nahuatl del Guerrero central", by Jonathan Amith, which includes a collection of 129 riddles from the area. It is in vol. XII of Tlalocan, (the most recent volume) published by the Instituto de Investigaciones Filologicas of the UNAM.