TY - RPRT TI - Letter Circular 760: information on ultraviolet transparency of window materials and fabrics (supersedes Letter Circular 235, 429, 511, and 549, and Form Letter 113) PY - 1944 PB - National Institute of Standards and Technology CY - Gaithersburg, MD SN - LCIRC 760 DO - 10.6028/NBS.LCIRC.760 ER -