Question: Joe gray was technical advisor to an actor who was considered "maybe the greatest actor who ever appeared in front of a camera" by who? 
Sentence (from "Joe Gray (actor)"): Joe Gray (May 5, 1912 – March 15, 1971) was an American boxer, actor and stuntman who made appearances in over 110 films in numerous uncredited roles, including 10 of Frank Sinatra's films and 32 of Dean Martin's films.
Relevant evidence: No