Is there any proof that lord krishna ever existed/lived?

What is the difference between a journal entry written by an eyewitness to an event and a play written about the same event? a. the journal entry is a historiographical source, while the play is a periodical source. b. the journal entry is a chronological source, while the play is a primary source. c. the journal entry is a primary source, while the play is a secondary source. d. the journal entry is a secondary source, while the play is a periodical source.