A handwriting expert says the two signatures on purported Texas National Guard memos aired by CBS News this week are not those of President Bush's squadron commander, as asserted by "60 Minutes." Until now, press scrutiny of the memos supposedly written by the late Lt. Col. Jerry B. Killian focused on the finding that the documents were, in the opinion of experts, produced by computers not yet in use in the early 1970s. Eugene P. Hussey, a certified forensic document examiner in Washington state, said yesterday there is another flaw in the CBS memos. Mr. Hussey studied the known signatures...