By R. Kent Dybvig; Prentice Hall, 1996, ISBN 0134546466, 2nd edition. Reference book, describes R5RS Scheme in style similar to K and R [Online full text version].
A complete Scheme system that is fully compatible with Chez Scheme but uses high-speed threaded interpreter technology in place of Chez Scheme's incremental native-code compiler. [Freeware]