TY  - RPRT
TI  - Circular of the Bureau of Standards no. 168: United States government master specification for asphalt for unsurfaced built-up roofing
PY  - 1924
PB  - National Bureau of Standards
CY  - Gaithersburg, MD
SN  - NBS CIRC 168
DO  - 10.6028/NBS.CIRC.168
ER  -