TY  - RPRT
TI  - Letter Circular 581: color of illuminant and efficiency of the worker (superseding Letter Circular 352)
PY  - 1940
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 581
DO  - 10.6028/NBS.LCIRC.581
ER  -