- Islandora Repository
- Mss.B.B61_W
- Warburg, Felix M.: From Boas. 1924 Oct. 31
- Warburg, Felix M.: From Boas. 1924 Oct. 9
- Warburg, Felix M.: From Boas. 1925 Nov. 10
- Warburg, Felix M.: From Boas. 1925 Nov. 3
- Warburg, Felix M.: From Boas. 1926 June 26
- Warburg, Felix M.: From Boas. 1927 Dec. 21
- Warburg, Felix M.: From Boas. 1927 Nov. 4
- Warburg, Felix M.: From Boas. 1928 May 23
- Warburg, Felix M.: From Boas. 1933 Dec. 12
- Warburg, Felix M.: From Boas. 1933 July 5
- Warburg, Felix M.: From Boas. 1933 Nov. 24
- Warburg, Felix M.: From Boas. 1933 Oct. 4
