Open-mid central unrounded vowel (English Wikipedia)

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Wissing (2012), p. 711. Wissing, Daan (2012), "Integrasie van artikulatoriese en akoestiese eienskappe van vokale: 'n beskrywingsraamwerk", LitNet Akademies (in Afrikaans), 9 (2), Stellenbosch: LitNet: 701–743, ISSN 1995-5928, archived from the original on 15 April 2017, retrieved 16 April 2017

Khan & Weise (2013), p. 236. Khan, Sameer ud Dowla; Weise, Constanze (2013), "Upper Saxon (Chemnitz dialect)" (PDF), Journal of the International Phonetic Association, 43 (2): 231–241, doi:10.1017/S0025100313000145

Kerr (1988), pp. 110, 113. Kerr, Harland (1988), "Cotabato Manobo Grammar" (PDF), Studies in Philippine Linguistics, 7 (1): 1–123, archived from the original (PDF) on 2015-05-11
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Allison (1979), p. 82. Allison, E. Joseph (1979), "The phonology of Sibutu Sama: A language of the southern Philippines" (PDF), Studies in Philippine Linguistics, 3 (2): 63–104, archived from the original (PDF) on 2015-05-11

Wissing (2016), section "The rounded and unrounded mid-central vowels". Wissing, Daan (2016). "Afrikaans phonology – segment inventory". Taalportaal. Archived from the original on 15 April 2017. Retrieved 16 April 2017.

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Jolkesky (2009), pp. 676, 682. Jolkesky, Marcelo Pinho de Valhery (2009), "Fonologia e prosódia do Kaingáng falado em Cacique Doble", Anais do SETA, 3, Campinas: Editora do IEL-UNICAMP: 675–685

Wissing (2012), p. 711. Wissing, Daan (2012), "Integrasie van artikulatoriese en akoestiese eienskappe van vokale: 'n beskrywingsraamwerk", LitNet Akademies (in Afrikaans), 9 (2), Stellenbosch: LitNet: 701–743, ISSN 1995-5928, archived from the original on 15 April 2017, retrieved 16 April 2017
Wissing (2016), section "The rounded and unrounded mid-central vowels". Wissing, Daan (2016). "Afrikaans phonology – segment inventory". Taalportaal. Archived from the original on 15 April 2017. Retrieved 16 April 2017.
Kerr (1988), pp. 110, 113. Kerr, Harland (1988), "Cotabato Manobo Grammar" (PDF), Studies in Philippine Linguistics, 7 (1): 1–123, archived from the original (PDF) on 2015-05-11
Wendel & Wendel (1978), p. 198. Wendel, Åsa; Wendel, Dag (1978), "Kaagan-Kalagan phonemic statement" (PDF), Studies in Philippine Linguistics, 2 (1): 191–203, archived from the original (PDF) on 2015-05-11
Allison (1979), p. 82. Allison, E. Joseph (1979), "The phonology of Sibutu Sama: A language of the southern Philippines" (PDF), Studies in Philippine Linguistics, 3 (2): 63–104, archived from the original (PDF) on 2015-05-11

Wissing (2012), p. 711. Wissing, Daan (2012), "Integrasie van artikulatoriese en akoestiese eienskappe van vokale: 'n beskrywingsraamwerk", LitNet Akademies (in Afrikaans), 9 (2), Stellenbosch: LitNet: 701–743, ISSN 1995-5928, archived from the original on 15 April 2017, retrieved 16 April 2017
Thomas (2001), pp. 27–28. Thomas, Erik R. (2001), An acoustic analysis of vowel variation in New World English, Publication of the American Dialect Society, vol. 85, Duke University Press for the American Dialect Society, ISSN 0002-8207