TY  - RPRT
TI  - Letter Circular 929: standards for checking the calibration of spectrophotometers (200 to 1000 m?)
PY  - 1948
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 929
DO  - 10.6028/NBS.LCIRC.929
ER  -