Railroad Archives Online
- FondoE0477 - BNSF Maps, Drawings and Records Collection
- Serie003 - Great Northern Railway Company (U.S.)
- Sottoserie009 - Engineering Records
- 008 - Tunnels
- Unità documentariaEBP0955 - Great Northern Technical Drawing, Cascade Tunnel, Washington, 1926
- Unità documentariaEBP0959 - Great Northern Technical Drawing, Cascade Tunnel, Washington, 1926
- Unità documentariaEBP0965 - Great Northern Technical Drawing, Cascade Tunnel, Washington, 1926
- Unità documentariaEBP0966 - Great Northern Technical Drawing, Cascade Tunnel, Washington, 1926
- Unità documentariaEBP4377 - Montana Central Railway Tunnel Technical Drawing, 1911