8Schaer S. Mapping and Predicting the Earth's Ionosphere Using the Global Positioning System [ D ]. Bern: The U- niversity of Bern, 1999.
9Bhuyan P K, Borah R R . TEC Derived from GPS Net- work in India and Comparison with the IRI [ J ]. Advances in Space Research, 2007, 39(5) :830 - 840.
10MENG Xiangping, GAO Yan. Electric systems analysis [M]. Beijing: Higher Education Press, 2004.