On evaluation of the mean gravity gradient within the topographyTenzer, Robert; Ellmann, ArtuObserving our changing Earth : proceedings of the 2007 IAG General Assembly : Perugia, Italy, July 2-13, 20072009 / p. 253-261 : ill https://www.researchgate.net/publication/226879587_On_Evaluation_of_the_Mean_Gravity_Gradient_Within_the_Topography