preface and intro. Added Matthew Flatt to the acknowledgements. original commit: 332e015dc2cd96160c468278def7d3b2cf8a1131
7.ss, scheme.1.in, comments of many files original commit: 06f858f9a505b9d6fb6ca1ac97234927cb2dc641
original commit: 47a210c15c63ba9677852269447bd2f2598b51fe