Railroad Archives Online
- CollectionD0036 - George Werkema Collection
- Series003 - Great Northern Railway Company (U.S.)
- Subseries Level 1014 - Photographs
- Subseries Level 2001 - Railroads--Equipment and Supplies
- Subseries Level 3006 - Cabooses (Railroads)
- Itemimg193 - Great Northern Caboose X47 at Wenatchee, Washington, 1968
- Itemimg194 - Great Northern Caboose X63 at Denver, Colorado, 1971
- Itemimg198 - Great Northern Caboose X101, 1970
- Itemimg199 - Great Northern Caboose X101, undated
- Itemimg200 - Great Northern Caboose X101, undated
- Itemimg201 - Great Northern Caboose X105 at Wenatchee, Washington, 1988
- Itemimg205 - Great Northern Caboose X224, undated
- 16 more...