E. J. Dobson (English pronunciation, 1500–1700, Oxford: Clarendon Press, 1968, passim) and other scholars before him postulated the existence of a vowel /y/ beside /iu̯/ in early Modern English. But see Fausto Cercignani, On the alleged existence of a vowel /y:/ in early Modern English, in "English Language and Linguistics", 26/2, 2022, pp. 263–277 [1]
doi.org
Roach (2004), p. 242. Roach, Peter (2004), "British English: Received Pronunciation", Journal of the International Phonetic Association, 34 (2): 239–245, doi:10.1017/S0025100304001768 (inactive 1 December 2024){{citation}}: CS1 maint: DOI inactive as of December 2024 (link)