- Islandora Repository
- Mss.B.B61_E
- Efrón, David: To Boas. 1939 Feb. 7
- Efrón, David: To Boas. 1939 July 22
- Efrón, David: To Boas. 1939 July 28
- Efrón, David: To Boas. 1939 July 7
- Efrón, David: To Boas. 1939 June 16
- Efrón, David: To Boas. 1939 Mar. 18
- Efrón, David: To Boas. 1939 Mar. 3
- Efrón, David: To Boas. 1939 Mar. 30
- Efrón, David: To Boas. 1939 Sept. 28
- Efrón, David: To Boas. 1940 Dec. 8
- Efrón, David: To Boas. 1940 July 2
- Efrón, David: To Boas. 1940 July 25
