TY  - RPRT
TI  - Letter Circular 511: information on ultraviolet transparency of window materials and fabrics (supersedes Letter Circular 235, 429, and 113)
PY  - 1938
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 511
DO  - 10.6028/NBS.LCIRC.511
ER  -