1. Report of investigations. 7916. Using sulfur hexafluoride as gaseous tracer to study ventilation systems in mines [with list of references]; by E. D. Thimons, R. J. Bielicki and F. N. Kissell. Bookmark Corporate/Agency Authors: Mines Bureau and Interior Dept. Publisher: Mines Bureau Date: [1974.] SuDoc number: I 28.28:7916