Martínez-Celdrán, Eugenio; Fernández-Planas, Ana Ma.; Carrera-Sabaté, Josefina (2003), "Castilian Spanish", Journal of the International Phonetic Association, 33 (2): 255–259, doi:10.1017/S0025100303001373
Rogers, Derek; d'Arcangeli, Luciana (2004), "Italian", Journal of the International Phonetic Association, 34 (1): 117–121, doi:10.1017/S0025100304001628