Possessive case when there are post nominal letters If a person's name comes with post nominal letters, e.g., John Smith PhD or Mary Green MD, which of the following is the correct/better way of forming the possessive?

(A): John Smith PhD's student; Mary Green MD's clcinc

(B): student of John Smith PhD; clinic of Mary Green MD

To me, style (A) sounds unnatural. So which is recommended?
You could go with:

Dr. Smith's student

and

Dr. Green's clinic