TY  - RPRT
TI  - Letter Circular 580: railway track scale testing service of the National Bureau of Standards fiscal year 1939 (July 1, 1938 to June 30, 1939)
PY  - 1939
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 580
DO  - 10.6028/NBS.LCIRC.580
ER  -