OPINION — AG — THOSE MEMBERS OF THE STATE EMPLOYEES RETIREMENT SYSTEM WHO HAVE SUBMITTED THE REQUIRE PROOF OF DISABILITY SET FORTH IN 74 O.S. 1976 Supp., 915 [74-915](B), MAY BE PAID BENEFITS RETROACTIVE TO DATE OF DISABILITY BUT NOT PRIOR TO THE DATE OF ENTITLEMENT AS ESTABLISHED BY THE SOCIAL SECURITY ADMINISTRATION AND FURTHER SUBJECT TO THE LIMITATIONS AS SET FORTH IN 74 O.S. 1976 Supp., 914 [74-914](3) (JAMES H. GRAY)