1. Howell, F. C., Nature, 219, 567 (1968).
2. Butzer, K. W., and Thurber, D. L., Nature, 222, 1139 (1969).
3. Butzer, K. W., and Brown, F. H., and Thurber, D. L., Quaternaria, 11 (in the press, 1970).
4. Butzer, K. W., Nature, 222, 1133 (1969).
5. Butzer, K. W., Troll-Festschrift, Erdkunde, 24 (in the press, 1970).