Research by experienced ethnologists began in the early 1900s when Robert Lowie visited the Chipewyan and when G. T. Emmons and James Teit studied the Tahltan and neighboring groups. A decade later, J. Alden Mason did field work among the Dogrib, while Kai BirketSmith paid a brief visit to the eastern Chipewyan, and Pliny Earle Goddard studied the Beaver. None of these scholars, all of whom are better known for their work among peoples other than Athapaskans, produced detailed ethnographic accounts, and in some cases their studies amount to little more than random ethnographic notes. Basic ethnographic data for many of the Athapaskan groups is lacking. The Koyukon are perhaps the least known, but the culture of some of the southern cordilleran groups is also far from completely understood, and researchers will have to rely heavily on ethnohistorie sources to supplement data from older informants.