Marcel Courthiade (1989) “The Common Romani Alphabet”, in Geoff Husič, transl.,Romani Grammar[1], e-book edition, volumes 1: General Information, Phonology, and Morphology, Lawrence, Kansas, published2019,→OCLC, page12
Yūsuke Sumi (2018) “Rr, rr”, inニューエクスプレス ロマ(ジプシー)語 [New Express Romani (Gypsy)] (in Japanese), Tokyo: Hakusuisha,→ISBN, page14