TY  - RPRT
TI  - Letter Circular 21 (Communication B521): the micrometer microscope and its uses in gage inspection
PY  - 1919
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 21
DO  - 10.6028/NBS.LCIRC.21
ER  -