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217 pages, Paperback
First published December 1, 1977
A funny thing happened to this book on the way to the publisher. More than two years ago, we had completed the manuscript of a book entitled Assaults on the Four-Color Conjecture... Our original book was oriented towards the variety of approaches with which the four-color conjecture (4CC for brevity) has been investigated. The reader can well imagine our mixed reactions to the announcement, in the summer of 1976, that the 4CC had been proved - by a computer, no less.They rewrote the book to focus on the newly discovered solution, and it's very interesting. People had been searching for an elegant, insightful proof, but the key turned out to be to use a machine to turn the problem into hundreds of special cases, and solve each one individually. The resulting proof is so long that only a machine can hope to be able to check its correctness.