Geochemistry of organic molecules: edited by Keith A. Kvenvolden, U.S. Geological Survey, Menlo Park, California, U.S.A. (Benchmark Papers in Geology, Vol. 52 Series Editor, Rhodes, W.) Fairbridge, Dowden, Hutchinson & Ross, Inc., Stroudsburg, Pennsylvania, U.S.A., 1980, xvi + 357 pp