Small-cap ⟨ᴜ⟩ was rounded to modern ⟨ʊ⟩ in 1904, but continued with its original shape in Americanist usage.Association phonétique internationale (1904). "Aim and Principles of the International Phonetic Association". Le Maître Phonétique. 19 (11). Supplement. JSTOR44703664.
openlibrary.org
Alphabet des langues nationales béninoises (in French). Ministère de l’Alphabétisation et de la Promotion des langues nationales, Centre national de linguistique appliquée, Benin. 2008. OL25931062M.