@misc{Efrat2001,
author = {Efrat, Alon and Hoffmann, Frank and Knauer, Christian and Kriegel, Klaus and Rote, Günter and Wenk, Carola},
year = {2001},
title = {Covering with ellipses},
howpublished = "http://dx.doi.org/10.17169/refubium-23185",
}