↑Hammarström, Harald; Forkel, Robert; Haspelmath, Martin, eds. (2017). "Southwestern Dutch". Glottolog 3.0. Jena, Germany: Max Planck Institute for the Science of Human History. {{cite book}}: Unknown parameter |chapterurl= ignored (help)
↑RL Trask, "Number of Languages", in Language and Linguistics: The Key Concepts, 2nd ed. 2007