1867 A. M. Bell 75 The ‘outer’ consonant corresponding to the ‘High-Front’ vowel, and the ‘inner’ to the ‘Low-Front’ vowel.
1934 J. J. Hogan 16 oi: mid-back rounded + high-front.
1994 J. Harkins vi. 161 The difference between the high front vowels of these two words, and the voicing distinction in their final stops, are neutralised.