Present participants can be asked directly to help spread the word. Toward the end of a series they can be asked to write on small cards the names and addresses of friends they think would be interested in receiving the announcement of the next series. Or, when present participants are mailed their copies of the new announcements, an extra copy can be enclosed and the covering letter can ask them to pass it along to someone else in their neighborhood or at work. Both devices have produced excellent results in actual practice.