This episode's headline: Looking for a Cause; Reviving Tax Reform; The Great Communicator; Smartening Up Textbooks; Iowa: After a Tragedy. The guests include In Ottawa: TOM HINTON, Canadian Air Safety Board; On Capitol Hill: Rep. ROBERT MICHEL, House Minority Leader; In San Francisco: BILL HONIG, California Education Superintendent; Reports from NewsHour Correspondents: WHIT FRASER (CBC), in Gander, Newfoundland; PHIL BELL (WTVF), Ft. Campbell, KY; STEPHEN TALBOTT (KQED), in California; KWAME HOLMAN, in Hills, Iowa. Byline: In New York: ROBERT MacNEIL, Executive Editor; CHARLAYNE HUNTER-GAULT, Correspondent