Clinical Reference Group (CRG) and the PH Service Specification Booklets Written by genius on Wednesday the 25th of February 2015. PHA UK have designed 2 new booklets to explain the Clinical Reference Group (CRG) and the PH Service Specification. To view the PDF versions of the booklets and to see the accompanying video, please see below. Download the PH Clinical Reference Group PDF (v2) Download the PH Service Specification PDF (v1)