9Salyer, Ival 0., Schwendeman, et al. Aqueous foam compositions to suppress coal dust[ P]. United States Pa- tent: 3954662, 1976-05-04.
10Tien, J. C. , and Kim, J.. Respirable coal dust control using surfactants [ J ]. Applied occupational and environ- mental hygiene, 1997, 12 (12) :957 - 963.