1. NASA. [accessed 23.03.09].
2. JAXA. [accessed 24.03.08].
3. JAXA. [accessed 24.03.08].
4. Discrete numerical model for granular assemblies;Cundall;Géotechnique,1979
5. Fujii H. An analysis of lugged wheel performance by DEM for the development of wheel for a lunar rover. Unpublished Master of Agricultural Sciences Thesis. Kyoto (Japan): Graduate School of Agriculture, Kyoto University; 2003.