I am trying to get a reference talking about /r/ discriminating power. Inside the paper I attached, at the end of section "previous work" it mentions that "Goldstein  shows that phonemes with free variants such as /r/ have a high speaker-discriminating content"
But the reference  is not in good format and I could not locate it .
Are you familiar with the reference "U. Goldstein 1975" ?
Thanks a lot,
A quantitative assessment of the relative speaker discriminatingproperties of phonemes.pdf
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