The Independent Subway System (IND; formerly the ISS
Sources
Books:
Periodicals:
- Electric Railroaders' Association: Headlights Magazine: August 1956, February 1968, February 1973, August 1974, July/September 1977, May/June 1988
Newspapers:
- The New York Times (before 1977), most notably: 1929: September 16, 22; 1932: September 4, 8, 9, 10; 1940: June 1, 2, 12, 13; 1967: November 22, 26, 28
- Unpublished document from New York City Transit Authority – precursor to "Facts and Figures", 1977