Books in the Grundriss der vergleichenden Grammatik der indogermanischen Sprachen 3 Volume Paperback Set series

Volume 1 of the monumental comparative grammar of the Indo-European languages by Karl Brugmann (1849-1919) is devoted to phonology. It focuses in turn on each Proto-Indo-European sound and its reflexes in the earliest attested languages of each language family, and also discusses Ablaut and sound changes.