TY  - RPRT
TI  - Background and objectives of the U.S. Standard for the colors of signal lights 
AU  - Breckenridge, F C
PY  - 1959
PB  - National Bureau of Standards
CY  - Gaithersburg, MD
SN  - NBS RPT 6413
DO  - 10.6028/NBS.RPT.6413
ER  -