Railroad Archives Online
- CollectionD0018 - Robert E. Kelly Collection
- Series003 - Great Northern Railway Company (U.S.)
- Subseries Level 1009 - Engineering Records
- Subseries Level 2006 - Painting and Lettering
- ItemW2021-012-005 - Great Northern Paint and Lettering Drawing, Series D Letters and Numbers, 1950
- ItemW2021-012-010 - Great Northern Paint and Lettering Drawing, Series C Letters and Numbers, 1951