Okada (1999), p. 118. Okada, Hideo (1999), «Japanese», in: International Phonetic Association, Handbook of the International Phonetic Association: A Guide to the Use of the International Phonetic Alphabet, ISBN978-0-52163751-0, Cambridge University Press, pp. 117–119
Henderson (1983), p. 595. Henderson, Michael M. T. (1983), «Four Varieties of Pashto», Journal of the American Oriental Society, 103 (3): 595–597, JSTOR602038, doi:10.2307/602038
Silverman et al. (1995), p. 83. Silverman, Daniel; Blankenship, Barbara; Kirk, Paul; Ladefoged, Peter (1995), «Phonetic Structures in Jalapa Mazatec», The Trustees of Indiana University, Anthropological Linguistics, 37 (1): 70–88, JSTOR30028043
Henderson (1983), p. 595. Henderson, Michael M. T. (1983), «Four Varieties of Pashto», Journal of the American Oriental Society, 103 (3): 595–597, JSTOR602038, doi:10.2307/602038