TY  - RPRT
TI  - Circular of the Bureau of Standards no. 391: stand thickness weights, and tolerances of sheet metal (customary practice)
PY  - 1931
PB  - National Bureau of Standards
CY  - Gaithersburg, MD
SN  - NBS CIRC 391
DO  - 10.6028/NBS.CIRC.391
ER  -