President doing his best to set limits on his own investigation — May 9, 1974If President Richard Nixon is to be impeached, he certainly is going to do all within his power to determine the limits of debate on the issue.He took a giant stride toward doing this with the release last week of 1,253 pages of excerpted transcripts of his Watergate-related conversations, a document which he claims tells the “full story of Watergate” and which, while causing him acute embarrassment, will clear him of complicity …