1. Cooper, M. R., Kovach, R. L., and Watkins, J. S.: 1974,Rev. Geophys. Space Phys. 12, 291?308.
2. Duennebier, F. K., Watkins, J., and Kovach, R.: 1974,Lunar Science V (abstract for the Fifth Lunar Conference), 183.
3. Johnson, D., Frisillo, A. L., Dorman, J., Latham, G., and Strangway, D.: 1975, in preparation.
4. Latham, G., Ewing, M., Press, F., and Sutton, G.: 1969,Science 165, 241?250.
5. Latham, G. V., Ewing, M., Press, F., Sutton, G., Dorman, J., Nakamura, Y., Toksöz, N., Lammlein, D., and Duennebier, F.: 1972,Apollo 16 Preliminary Science Report, NASA SP-315, 9.