The question of Hal Holbrook's performances of Mark Twain (available on cassette, but not on video) keeps coming up. THERE IS NO VIDEO TAPE OF HIS LEGENDARY "Mark Twain Tonight." I have heard rumors, however, that he may be redoing his performance sometime in the near future for a television special. If so, of course, we will all record the thing and never have to ask the question again. Joe McCullough