1. Anderson, D.R., Sweeney, D.J., Williams, T.A., 1993. Introduction to Statistics: Concepts and Applications, 3rd edn. West Publishing Company, Minnesota, USA, 903pp.
2. Defense Mapping Agency, 1987. Department of Defense World Geodetic System 1984: Its definition and relationships with local geodetic systems. Technical Report No. 8350.2, Defense Mapping Agency, Washington, DC, approx. 150pp.
3. Local geoid determination and comparison with GPS results;Denker;Bulletin Géodésiqué,1987
4. Measuring orthometric height differences with GPS and gravity data;Engelis;manuscripta geodaetica,1985
5. The precise computation of geoid undulation differences with comparison to results from the Global Positioning System;Engelis;Geophysical Research Letters,1984