The Dusty universe : proceedings of a symposium honoring Fred Lawrence Whipple on his retirement as director of the Smithsonian Astrophysical Observatory, October 17-19, 1973 - Whipple, Fred Lawrence; Field, George B.; Cameron, Alastair Graham Walter; Smithsonian Astrophysical Observatory (Published for the Smithsonian Astrophysical Observatory by Neale Watson Academic Publications, 1975)