Slezak, M. H. and El-Baz, Farouk. 1979. "Temporal Changes as Depicted on Orbital Photographs of Arid Regions in North Afriica." in Apollo-Soyuz Test Project Summary Science Report. Volume II: Earth Observations and Photography, NASA SP-412, edited by El-Baz, Farouk and Warner, Delia M., 263–272. Washington, D.C.: NASA Scientific and Technical Information Branch.