Railroad Archives Online
- CollectionD0011 - James M. Fredrickson Collection
- Series004 - Northern Pacific Railroad Company
- Subseries Level 1014 - Photographs
- Subseries Level 2001 - Railroads--Equipment and Supplies
- Subseries Level 3008 - Buses
- ItemJMF08-05409.0 - Northern Pacific Transport bus, number B41-20 at Tacoma, Washington, in 1960.
- ItemJMF08-05409.1 - Northern Pacific Transport bus, number B41-20 at Tacoma, Washington, in 1960.
- ItemJMF08-05415.0 - Northern Pacific Transport letter, July, 1956.
- ItemJMF08-05416.0 - Northern Pacific Transport bus, in 1956.
- ItemJMF08-05417.0 - Northern Pacific Transport bus, in 1956.
- ItemJMF08-05418.0 - Northern Pacific Transport bus, in 1956.
- ItemJMF08-05419.0 - Northern Pacific Transport bus, in 1956.