printed in 1963. The Minto data did appear in a series of IJAL articles by Krauss in the mid to late 1960s, but it was some time before the existence of an additional Proto-Athabaskan affricate series became widely known. Eyak Krauss' largest contribution to language documentation was his work on Eyak, which began in 1961. Eyak was then already the most endangered of the Alaskan languages, and Krauss' work might be considered salvage linguistics today. While some Eyak data had been previously available, they were overlooked by previous scholars, including Edward Sapir. However, Eyak proved to be a crucial missing link for historical linguistics, being equally closely related to neighboring Ahtna and to distant Navajo. With good Eyak data it became possible to establish the existence of the Athabaskan–Eyak–Tlingit language family, though phonological evidence for links to Haida remained elusive. Further, the system of vowel modifications present in Eyak inspired Krauss' theory of Athabaskan tonogenesis, whereby tone develops from vowel constriction. Endangered languages Michael Krauss' lecture at the Linguistic Society of America conference in January 1991 is often cited as a turning point which refocused the field of linguistics on documentation and inspired a systematic global effort to document the world's linguistic diversity. In his lecture, titled "The world's languages in crisis," Dr. Krauss famously warned: Michael Krauss contends that in the United States, children are only learning 20% of the world's remaining languages. Selected bibliography Monographs Krauss, Michael E. (n.d.). Na-Dene. College, AK: University of Alaska and M.I.T. Krauss, Michael E. (1969). On the classification in the Athapascan, Eyak, and the Tlingit verb. Baltimore: Waverly Press, Indiana University. Krauss, Michael E. (1970). Eyak dictionary. College, AK: University of Alaska. Krauss, Michael E. (1970). Eyak texts. College, AK: University of Alaska and Massachusetts Institute of Technology. Krauss, Michael E. (1970). Eskimo–Aleut. The Hague: Mouton. Krauss, Michael E. (1974). Native peoples and language of Alaska. Fairbanks, AK: Alaska Native Language Center, Center for Northern Educational Research, University of Alaska. Krauss, Michael E. (1980). Alaska native languages: Past, present, and future. Fairbanks, AK: Alaska Native Language Center. Krauss, Michael E. (1980). On the history and use comparative Athapaskan linguistics. Fairbanks, AK: University of Alaska, Native Language Center. Krauss, Michael E. (1985). Yupik Eskimo prosodic systems: Descriptive and comparative studies. Fairbanks, AK: Alaska Native Language Center. Articles Krauss, Michael E. (1973). Na-Dene. In T. A. Sebeok (Ed.), Linguistics in North America (pp. 903–978).