where did you find alexander butterfield? >> guest: umm, oh, some of thement -- them we found through google or people who knew people. we put out the word that we were doing these. initially the nixon foundation -- the private nixon foundation provided the funding for the first group. i was upfront about what we were doing. i promised the things nixon foundation and the federal government we could a nonpartisan oral history program. >> host: we don't see you in the interviews. >> guest: that's by choice. i remember going an l.a. festival of the book, i listened to david hall we -- it was in 2005. before i got this job -- that job. i'm not there anymore. he was talking about the best interview. he said the best interviewer is the peers. and i thought, what i would do would be to disappear. that my job would be to help the interviewee recall events to encourage them and create a zone of comfort, but to disappear. also, because the goal was for this to be video that could be used for documentaries in the future, as well as for

. >> schieffer: nixon aide alexander butterfield at the senate watergate hearings 40 years ago revealing existence of a white house taping system. today, the national archives released the last of the tapes secretly recorded by president richard nixon. bill plante has been listening in. >> i'm not a crook. >> reporter: in the spring of 1973, richard nixon was consumed with watergate. his national secure advisor, henry kissinger, assured him no one would remember. but white house counsel john dean had been called before a senate committee. by the end of april, nixon was ready to fire dean and let his two top aides, bob haldeman and john ehrlichman, resign. he spoked to haldeman. following the speech, the president spent the rest of the night taking calls of support. this one from california governor ronald reagan. a call from the reverend billy graham. nixon asked about tv coverage of the speech. in the midst, nixon was instructing diplomat david bruce, his envoy to china. three months before anyone knew about the white house taping system, nixon asked haldeman to destroy the tapes. for w