TY  - RPRT
TI  - Letter Circular 822: National Bureau of Standards specification for proving rings for calibrating testing machines (superseding Letter Circular 657)
PY  - 1946
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 822
DO  - 10.6028/NBS.LCIRC.822
ER  -