TY - RPRT TI - Optical radiation measurements: development of an NBS reference spectrophotometer for diffuse transmittance and reflectance AU - Hsia, Jack J AU - Venable Jr, William H AU - Weidner, Victor R PY - 1976 PB - National Bureau of Standards CY - Gaithersburg, MD SN - NBS TN 594-11 DO - 10.6028/NBS.TN.594-11 ER -