Luyen, Bui Khac. “REFINING GEOIDAL HEIGHTS COMPUTED BY FULLY-NORMALISED SPHERICAL HARMONICS COEFFICIENTS OF THE EARTH GRAVITATIONAL MODEL EGM2008 BY ADJUSTMENT OF COMBINED GPS LEVELLING GEOID NETWORK”. Vietnam Journal of Earth Sciences, vol. 36, no. 2, Aug. 2014, pp. 169-74, doi:10.15625/0866-7187/36/2/4498.