Anttila, Raimo. Proto-Indo-European schwebeablaut / by Raimo Anttila. - Berkeley ; Los Angeles : University of California Press, 1969. - xvii, 238 p. 26 cm. - University of California publications in linguistics v. 58 . - 410 . A revision of the author's thesis, Yale, 1966. Bibliography: p. 179-194. Subjects--Topical Terms: Proto-Indo-European language--Vowel gradation.Indo-European languages--Vowel gradation. Dewey Class. No.: 410