"Några bidrag till fornnordisk grammatik", Arkiv för nordisk filologi. Ny följd. Andra bandet. Kluge (1889). "Vorgeschichte der Altgermanichsen Dialekte", Grundriss der germanischen Philologie, herausgegeben von Herman Paul. Strassburg, Trübner. Lloyd L. (1966). "Is there an a-umlaut of i in Germanic?", Language 42:4, pp. 738–745. Sturtevant (1956). "The a-umlaut of the radical vowel i in Old Norse monosyllabic stems", Modern Language Notes 71:3, pp. 194–200. Wright (1917). Grammar of the Gothic Language. Oxford University Press. See also I-mutation Germanic umlaut Vowel harmony Sound laws Vowel shifts Germanic languages