1. Letter from Ralph M. Waters to Virginia Apgar Creator: Waters, Ralph M.The University of Wisconsin. State of Wisconsin General Hospital Date: 27 April 1936 Genre: Letters (correspondence)
2. Letter from Ralph M. Waters to Virginia Apgar Creator: Waters, Ralph M.The University of Wisconsin. State of Wisconsin General Hospital Date: 29 October 1936 Genre: Letters (correspondence)
3. Letter from Ralph M. Waters to Virginia Apgar Creator: Waters, Ralph M.The University of Wisconsin. State of Wisconsin General Hospital Date: 6 January 1939 Genre: Letters (correspondence)
4. Letter from Ralph M. Waters to Virginia Apgar Creator: Waters, Ralph M.The University of Wisconsin. State of Wisconsin General Hospital Date: 5 March 1938 Genre: Letters (correspondence)