1. Letter from Donald S. Fredrickson to Daniel E. Koshland, Jr Publication: Produced: 23 August 1976 Subject(s): National Academy of Sciences (U.S.)Plasmids Archival Collection: The Maxine Singer Papers (Profiles in Science)
2. Letter from Joshua Lederberg to Gail Cassell Publication: Produced: 30 April 1999 Subject(s): PlasmidsDrug Resistance, MicrobialAnti-Bacterial Agents Archival Collection: The Joshua Lederberg Papers (Profiles in Science)
3. Letter from Harold Varmus to Robert A. Weinberg, Massachusetts Institute of Technology Publication: Produced: 17 June 1983 Subject(s): Clone CellsPlasmidsIndicators and Reagents Archival Collection: The Harold Varmus Papers (Profiles in Science)
