TY - RPRT TI - Letter Circular 619: standards and specifications for building and construction materials, fixtures, supplies, and equipment (superseding Letter Circular 570) PY - 1940 PB - National Institute of Standards and Technology CY - Gaithersburg, MD SN - LCIRC 619r1940 DO - 10.6028/NBS.LCIRC.619r1940 ER -