^Gordon, Matthew (2004), “The West and Midwest: phonology”, in Kortmann, Bernd, A Handbook of Varieties of English: Volume 1: Phonology, Walter de Gruyter, p. 340, ISBN3110175320
^Tillery, Jan and Guy Bailey, “The urban South: phonology”, in Kortmann, Bernd, A Handbook of Varieties of English: Volume 1: Phonology, Walter de Gruyter, p. 333, ISBN3110175320