Journalist and urban critic Roberta Brandes Gratz and an expert in downtown revitalization Norman Mintz. The two have collaborated on the new book "Cities: Back from the Edge: New Life for Downtown." (John Wiley & Sons). In the book they look at downtowns throughout the country that have come back to life and examine what revived them. Their recipe for success includes: preserving or introducing trolley traffic, developing farmers' markets, promoting short blocks, keeping government buildings downtown, and insuring citizen involvement in civic life.