Martínez-Celdrán (2004:201) Martínez-Celdrán, Eugenio (2004), “Problems in the classification of approximants”, Journal of the International Phonetic Association, 34 (2): 201–210, doi:10.1017/S0025100304001732
Martínez-Celdrán (2004:201), pointing to Ladefoged (1964:25) Martínez-Celdrán, Eugenio (2004), “Problems in the classification of approximants”, Journal of the International Phonetic Association, 34 (2): 201–210, doi:10.1017/S0025100304001732Ladefoged, Peter (1964), A Phonetic Study of West African Languages, Cambridge: Cambridge University Press