Engstrand (1999),第140頁. Elmquist (1915),第33頁. Árnason, Kristján, The Phonology of Icelandic and Faroese, Oxford University Press, 2011, ISBN 978-0-19-922931-4
2010 [2018-04-08], (原始内容 (PDF)存档于2018-11-01) Árnason, Kristján, The Phonology of Icelandic and Faroese, Oxford University Press, 2011, ISBN 978-0-19-922931-4
the Historical Phonology of Ossetic." Journal of the American Oriental Society, Vol. 123, No. 1. (Jan.-Mar.,2003) Karlsson, Fred. Finnish - A Comprehensive
ISBN 978-0-521-71740-3 Siptár, Péter; Törkenczy, Miklós, The Phonology of Hungarian, The Phonology of the World's Languages, Oxford University Press, 2007