The Triques, Amuszos and Cuicatecos are related to the Mixtecs and have similar languages, The Chochopopolocas and Ixcatecos are similar to the Mazatecos; the Zoques are related to the Mixes, and the Chatinos are related to the Zapotecs.
To these followed sundry studies, published as monographs or articles, on the languages and traditions of the Ch'ol, Mangue, Nahua, Yucatec Maya, and Zoque.