1. Boaz, N. T., Howell, F. C. & McCrossin, M. L. Nature 300, 633–635 (1982).
2. Cooke, H. B. S. Kirtlandia 29, 1–63 (1978).
3. Cerling, T. E. & Brown, F. H. Nature 299, 216–221 (1982).
4. Brown, F. H. Calibration of Hominoid Evolution (eds Bishop, W. W. & Miller, J. A.) 273–287 (Scottish Academic, Edinburgh, 1972).
5. Johanson, D. C., Taieb, M., Gray, B. T. & Coppens, Y. Geological Background to Fossil Man (ed. Bishop, W. W.) 549–564 (Scottish Academic, Edinburgh, 1978).