Информация
Sources
1. Randolph L. Kulp (Editor). 
History of Lehigh Valley Transit Company: railway operations. Allentown, PA: Lehigh Valley Chapter NRHS, 1966. 
2. Randolph L. Kulp (Editor). 
Short Trolley Routes in the Lehigh River Valley. Allentown, PA: Lehigh Valley Chapter NRHS, 1967.
3. Randolph L. Kulp (Editor). 
The Lehigh Valley Transit Company's St. Louis cars: history and roster. Allentown, PA: Lehigh Valley Chapter NRHS, 1961.
4. Randolph L. Kulp (Editor). 
Liberty Bell Route's Heavy Interurban Cars: History and Rosters. Allentown, PA: Lehigh Valley Chapter NRHS, 1969.
5. Randolph L. Kulp (Editor). 
The Liberty Bell Route's 800 Series Interurbans: History and Roster. Allentown, PA: Lehigh Valley Chapter NRHS, 1958.
6. Randolph L. Kulp (Editor). 
The Liberty Bell Route's 1000 Series, Interurban Cars: History and Roster. Allentown, PA: Lehigh Valley Chapter NRHS, 1964.
7. Harold E. Cox. 
The Birney Car. Forty Fort, PA: Author, 1966.
 
8. Alan Lind. 
From Horsecars to Streamliners: An Illustrated History of the St. Louis Car Company. Park Forest, IL: Transport History Press, 1978.
9. Lawrence A. Brough and James H. Graebner. 
From Small Town to Downtown: A History of the Jewett Car Company, 1893-1919 (Railroads Past and Present). Indiana University Press, 2004.  
 
See also 
http://streetcars.telcen.com/ — a personal site of Dr. Harold E. Cox with author’s books and car builders’ order lists.