TY  - RPRT
TI  - Supplement to circular no. 25: standard samples issued or in preparation
PY  - 1927
PB  - National Bureau of Standards
CY  - Gaithersburg, MD
SN  - NBS CIRC 25sup-1927
DO  - 10.6028/NBS.CIRC.25sup-1927
ER  -