Sergio Cabello José Miguel Díaz-Báñez Carlos Seara Joan Antoni Sellarès Jorge Urrutia Inmaculada Ventura Covering point sets with two disjoint disks or squares. 195-206 2008 40 Comput. Geom. 3 http://dx.doi.org/10.1016/j.comgeo.2007.10.001 db/journals/comgeo/comgeo40.html#CabelloDSSUV08