TY  - RPRT
TI  - Letter Circular 644: list of commercial standards (supersedes Letter Circular 624)
PY  - 1941
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 644r1941
DO  - 10.6028/NBS.LCIRC.644r1941
ER  -