[…] on the basis of chapter 7 [phonemes] we would have to recognize at least two sets of vowels, distinguished chiefly by length and type of off-glide. There would be /ay/ of 'minus' and /Ay/ of 'slyness', /ey/ of 'playful' and /Ey/ of 'tray-ful', and so on. Members of the shorter or less drawled set do not occur at the end of an utterance. Such general limitations of occurrence affecting one of two parallel sets of tentative phonemes leads us to ask whether the limitation may not be avoided and the two sets somehow made into one.
- Harris (1951), a pag.79