9Bevis M, Businger S, Chiswell S R, et al. GPS meterolo- gy: mapping zenith wet delays onto precipitable water [J]. Appl. Meteor, 1994, 33(3): 379-386.
10Duan J, Bevis M, et al. GPS Meteorology: direct estima- tion of the absolute precipilable water [ J]. Journal of Ap- plied Meteorology, 1996, 35 (6) : 830 - 838.