copyright notice for text files **** Copyright 1985-1994 by The Massachusetts Institute of Technology All rights reserved. These sample problem sets, or parts thereof, may be reproduced for use with Structure and Interpretation of Computer Programs by Harold Abelson and Gerald Jay Sussman with Julie Sussman MIT Press, 1985 provided such reproductions bear copyright notice, but may not be reproduced in any form for any other purpose without permission of the publisher. ****