1. Li Z H, Chen K, Liu W K, et al. Ionospheric delay model containing f3 term (in Chinese). Geomat Inf Sci Wuhan Univ, 2007, 32: 139–143
2. Liu Q, Zhang X, Zhu Y P. GPS triple-frequency methods of highorder Ionospheric refraction correction (in Chinese). Geomat Inf Sci Wuhan Univ, 2006, 9: 41–46
3. Wu Y, Meng Y, Wang Z M, et al. Triple-frequency methods for correcting higher-order ionospheric refractive error in GPS modernization (in Chinese). Geomat Inf Sci Wuhan Univ, 2005, 30: 601–608
4. Wang Z M, Wu Y, Zhang K F, et al. Triple-frequency method for high-order ionospheric refractive error modeling in GPS modernization. J Glob Position Syst, 2005, 4: 291–295
5. Bassiri S, Hajj G A. Higher-order ionospheric effects on the global positioning system observables and means of modeling them. Manuscr Geod, 1993, 18: 280–289