Railroad Archives Online
- CollectionD0027 - Timothy Miller Collection
- Series007 - Spokane, Portland, and Seattle Railway
- Subseries Level 1009 - Engineering Records
- Subseries Level 2008 - Physical plant drawing
- Subseries Level 3005 - Signals
- ItemStruc008757 - Spokane, Portland, and Seattle Railway Engineering Drawing, Microwave Tower 100 Foot at Portland, Oregon, 1970
- ItemStruc009223 - Spokane, Portland, and Seattle Railway Engineering Drawing, Signal Maintainer's Tool House at Willbridge, Oregon, 1952