Railroad Archives Online
- FondD0046 - Andrew Klamka Collection
- Sorozat003 - Great Northern Railway Company (U.S.)
- Alsorozat004 - Library
- 002 - Periodicals
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- IratdarabGNSemaphoreVol5No7 - 'Great Northern Semaphore' July 1928
- IratdarabGNSemaphoreVol5No8 - 'Great Northern Semaphore' August 1928
- IratdarabGNSemaphoreVol5No9 - 'Great Northern Semaphore' September 1928
- IratdarabGNSemaphoreVol5No10 - 'Great Northern Semaphore' October 1928
- IratdarabGNSemaphoreVol5No11 - 'Great Northern Semaphore' November 1928
- IratdarabGNSemaphoreVol5No12 - 'Great Northern Semaphore' December 1928