21. Letter from Max Delbruck, California Institute of Technology to Michael Heidelberger Publication: Produced: 16 March 1938 Subject(s): Antigen-Antibody ReactionsPrecipitins Archival Collection: The Michael Heidelberger Papers (Profiles in Science)
22. Letter from Michael Heidelberger to Max Delbruck, California Institute of Technology Publication: Produced: 28 March 1938 Subject(s): Antigen-Antibody Reactions Archival Collection: The Michael Heidelberger Papers (Profiles in Science)