TY  - RPRT
TI  - Letter Circular 930: standards of length, mass, and time (supersedes Letter Circular 449)
PY  - 1949
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 930
DO  - 10.6028/NBS.LCIRC.930
ER  -