1. Baedecker, P. A., Chou, C. L., Grudewicz, E. B., and Wasson, J. L.: 1973, 4th Lunar Sci. Conf. Abs. 45.
2. Baldwin, R. B.: 1971, Icarus 14, 36.
3. Baldwin, R. B.: 1970, Science 170, 1297.
4. Basilevsky, A. T., Ronca, L. B., and Ivanov, B. A.: 1980, Moon and Planets 23, 335.
5. Boud, A. (n�e Tyrie): 1982, Proc. Int. Soc. for Photogr. and Remote Sensing, Comm. II Symp. Int. Arch. of Photogr. 24?11, 225?236.