>> mr. butterfield, are you aware of the installation of any devices, listening devices, in the oval office of the president? >> i was aware of listening devices, yes, sir. >> on whose authority were they installed, mr. butterfield? >> on the president's authority for posterity. >> all right. mr. butterfield, as far as you know from your own personal knowledge, all of the president's conversations were recorded? as far as you know. >> that's correct. >> mr. butterfield, if one were to reconstruct the conversations, what would be the best way to reconstruct those conversations? >> well, in the obvious manner, mr. dash, to obtain the tape and play it.