Railroad Archives Online
- FondsD0036 - George Werkema Collection
- Serie001 - Burlington Northern Railroad Company
- Teilserie014 - Photographs
- 001 - Railroads--Equipment and Supplies
- 004 - Railroad Passenger Cars
- ObjektWerkema378 - Burlington Northern railway post office car 1931 in 1973.
- Objektimg322 - Burlington Northern Passenger Car at Denver, Colorado, 1981
- Objektimg323 - Burlington Northern Passenger Car at Denver, Colorado, 1981
- Objektimg324 - Burlington Northern Passenger Car at Denver, Colorado, 1985