1. Letter from Colin M. MacLeod to Michael Heidelberger Publication: Produced: 20 May 1941 Subject(s): VaccinesPolysaccharidesPneumococcal Infections Archival Collection: The Michael Heidelberger Papers (Profiles in Science)
2. Letter from Arie C. Van Ravenswaay, United States Army Air Forces to Michael Heidelberger Publication: Produced: 1 June 1944 Subject(s): VaccinesPneumococcal Infections Archival Collection: The Michael Heidelberger Papers (Profiles in Science)
3. Letter from Colin M. MacLeod to United States Army, Office of the Surgeon General Publication: Produced: 3 July 1944 Subject(s): VaccinesClinical Trials as TopicPneumococcal Infections Archival Collection: The Michael Heidelberger Papers (Profiles in Science)
