by the U.S. Department of the Interior, U.S. Geological Survey (Published in hardcopy as USGS Miscellaneous Investigations Series Map I–1660, as part of the Atlas of Mercury, 1:5,000,000 Geologic Series. Hardcopy is available for sale from U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225) References Boyce, J. M., Dial, A. L., and Masursky, Harold, 1976, The optimal sun angle for obtaining photographs of martian surface features from orbit: U.S. Geological Survey Interagency Report: Astrogeology 78, 8 p. Boyce, J. M., and Grolier, M. J., 1977, The geology of the Goethe (H-l) quadrangle of Mercury, in Arvidson, Raymond, and Wahmann, Russell, eds., Reports of planetary geology program, 1976–1977: National Aeronautics and Space Administration Technical Memorandum X-3511, p. 237. Cintala, M. J., Wood, C. A., and Head, J. W., 1977, The effects of target characteristics on fresh crater morphology: Preliminary results for the moon and Mercury: Lunar Science Conference, 8th, Houston, 1977, Proceedings, p. 3409–3425, 4 figs., 3 tables. Colombo, Giuseppe, 1965, Rotational period of the planet Mercury: Nature, v. 208, no. 5010, p. 575. Colombo, Giuseppe, and Shapiro, I. I., 1966, The rotation of the planet Mercury: The Astrophysical Journal, v. 145, p. 296–307. De Hon, R. A., Scott, D. H., and Underwood, J. R., Jr., 1981, Geologic map of the Kuiper quadrangle of Mercury; U.S. Geological Survey Miscellaneous Investigations Series Map I-1233, scale 1:5,000,000. Dzurisin, Daniel, 1978, The tectonic and volcanic history of Mercury as inferred from studies of scarps, ridges, troughs, and other lineaments: Journal of Geophysical Research, v. 83, no. B10, p. 4883–4906. Guest, J. E., and Greeley, Ronald, 1983, Geologic map of the Shakespeare quadrangle of Mercury: U.S. Geological Survey Miscellaneous Investigations Series Map I-1408, scale 1:5,000,000. Guest, J. E., and O’Donnell, W. P., 1977, Surface history of Mercury: A review: Vistas in Astronomy, v. 20, p. 273–300. Hapke, Bruce, 1977, Interpretations of optical observations of Mercury and the Moon: Physics of the Earth and Planetary Interiors, v. 15, p. 264– 274. Hapke, Bruce, Danielson, G. E., Jr., Klaasen, Kenneth, and Wilson, Lionel, 1975, Photometric observations of Mercury from Mariner 10: Journal of Geophysical Research, v. 80, no. 17, p. 2431–2443 Hartmann, W. K., 1966, Early lunar cratering: Icarus, v. 5, no.4, p. 406– 418. Hartmann, W. K., 1967, Lunar crater counts, III: Post mare and “Archimedean” variations: Lunar and Planetary Laboratory, Communication no. 116, v. 7, pt. 3, p. 125–129. Klaasen, K.