1971, Peter Ladefoged, Preliminaries to Linguistic Phonetics, page 15:
In these words, as in similar forms in related Chadic languages, laryngealized voicing is often audible in the adjacent vowels
2007, Anton Batliner, Richard Huber, “Speaker characteristics and emotion classification”, in Christian Müller, editor, Speaker Classification I, page 143:
It is well known that back vowels such as [ɑ] tend to be more laryngealized than front vowels such as [i] (local phenomenon).