Leiden : E.J. Brill
Majalah, Jurnal, Buletin
Wilhelm Braumuller,
Majalah, Jurnal, Buletin
Hannah Lewi, Wally Smith, Dirk Vom Lehn and Steven Cooke
Routledge, 2020
Buku Teks
Forde, Helen, author
Facet Publishing, 2007
Buku Teks
Vowels : J.P. Kelly and J.B. Heley
Majalah, Jurnal, Buletin