TY  - RPRT
TI  - Letter Circular 568: list of commercial standards (supersedes Letter Circular 557)
PY  - 1939
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 568r1939
DO  - 10.6028/NBS.LCIRC.568r1939
ER  -