Rujukan Gambar rajah vokal

  1. ↑ Ladefoged, Peter (1999). "American English". Handbook of the International Phonetic Association. Cambridge: Cambridge University Press. halaman 41–44. ISBN 0-521-63751-1.
  2. 1 2 3 Paul Skandera and Peter Burleigh (2005). A Manual of English Phonetics and Phonology. Gunter Narr Verlag. halaman 33–34. ISBN 3823361252.
  3. ↑ Cancio, Mary Lou (2007). Functional Phonetics Workbook. San Diego, CA: Plural Publishing.
  4. ↑ Russell, Kevin (27 November 2005). "Describing English vowels". Phonetics. University of Manitoba. Dicapai pada 18 April 2013.
  5. ↑ Eva M. Fernández and Helen Smith Cairns (2011). Fundamentals of Psycholinguistics. Wiley-Blackwell. halaman 158–159. ISBN 9781405191470.
  6. ↑ Heinz J. Giegerich (1992). English Phonology: An Introduction. Cambridge University Press. halaman 14–15. ISBN 0521336031.