- Árnason, Kristján, The Phonology of Icelandic and Faroese, Oxford University Press, 2011, ISBN 978-0-19-922931-4
- Keane, Elinor, Tamil, Journal of the International Phonetic Association, 2004, 34 (1): 111–116, doi:10.1017/S0025100304001549
- Sadowsky, Scott; Painequeo, Héctor; Salamanca, Gastón; Avelino, Heriberto, Mapudungun, Journal of the International Phonetic Association, 2013, 43 (1): 87–96, doi:10.1017/S0025100312000369
- Trudgill, Peter, The Sociophonetics of /l/ in the Greek of Sphakiá, Journal of the International Phonetic Association, 1989, 15 (2): 18–22, doi:10.1017/S0025100300002942
- ^ Sebregts, Koen. The Sociophonetics of and Phonology of Dutch r (PDF). : LOT. 2014. ISBN 978-94-6093-161-1.
- ^ 2.0 2.1 2.2 Árnason (2011:115)
- ^ Trudgill (1989:18–19)
- ^ Nas trilhas do -r retroflexo Silvia Figueiredo Brandão. December 2007. Retrieved June 19, 2015.
- ^ (in Portuguese) Acoustic-phonetic characteristics of the Brazilian Portuguese's retroflex /r/: data from respondents in Pato Branco, Paraná. Irineu da Silva Ferraz. Pages 19–21
- ^ (in Portuguese) Syllable coda /r/ in the "capital" of the paulista hinterland: sociolinguistic analisis. Cândida Mara Britto LEITE. Page 111 (page 2 in the attached PDF)
- ^ (in Portuguese) Callou, Dinah. Leite, Yonne. "Iniciação à Fonética e à Fonologia". Jorge Zahar Editora 2001, p. 24
- ^ Keane (2004:111)