Wiki Modifier -AH when the PhD is HSPP Certified

[bridgettemartin]

A few years ago I did extensive research on Modifier AH and discovered if the Clinical Psychologist was HSPP certified, this modifier was not applied. I have since misplaced my references for this, and the only thing I can find for CMS is just that the modifier is used to indicate services were provided by a clinical psychologist. Nothing about whether or not the psychologist is HSPP certified.
I did find on Anthem's policy is says: AH: clinical psychologist - (not licensed health service provider in Psychology - HSPP)
Does anyone have CMS references on this?

Much appreciated!