Mystery Still Surrounds J.F.K. Assassination, 36 Years
       Later

       Today marks the 36th anniversary of the death of President John F. Kennedy and
       even now there is mystery surrounding the details of his assassin. Hours after the
       president was shot, F.B.I. agents reportedly listened to a tape of a phone call that a
       man identifying himself as "Lee Oswald" had placed to the Soviet Embassy in Mexico
       City. Government records suggest the agents made a startling discovery -- the voice
       on the tape was not Oswald's. Several assassination researchers have some theories
       as to why anyone would impersonate Oswald. One theory is that a C.I.A. officer could
       have impersonated Oswald and called the Soviet Embassy to fish for details about
       what Oswald had recently been doing in Mexico City. Another is that someone may
       have been trying to link Oswald to the K.G.B.'s assassination unit.