Mícheál Ó Siadhail (1989) Modern Irish: Grammatical Structure and Dialectal Variation, Cambridge: Cambridge University Press, published 1991, →ISBN, page 318
Kuninao Nashimoto (2020 March) ニューエクスプレスプラス アイルランド語 [New Express Plus Irish] (in Japanese), Tokyo: Hakusuisha, →ISBN, pages 17-19