Sapir also encouraged Whorf to continue his work on the historical and descriptive linguistics of Uto-Aztecan. Whorf published several articles on that topic in this period, some of them with G. L. Trager, who had become his close friend. Whorf took a special interest in the Hopi language and started working with Ernest Naquayouma, a speaker of Hopi from Toreva village living in Manhattan, New York. Whorf credited Naquayouma as the source of most of his information on the Hopi language, although in 1938 he took a short field trip to the village of Mishongnovi, on the Second Mesa of the Hopi Reservation in Arizona.