Title An Atlas of regular thin geometries for small groups Author Dimitri Leemans Reference Math. Comput., 68(1999), nr. 228, 1631-1647. Math. Reviews 99m:51018 Zentralblatt 941.51010 Abstract For some small groups, we give, up to isomorphism, an exhaustive list of all residually connected thin geometries on which these groups act regularly. We then show the utility of such an atlas by proving several results about smallest groups acting on a given diagram. The results have been obtained using a series of {\sc Magma} programs.