@incollection{ref,
author = {Martin Stich and Carsten Wächter and Alexander Keller},
title = {Efficient and Robust Shadow Volumes Using Hierarchical Occlusion Culling and Geometry Shaders},
booktitle = {GPU Gems 3},
editor = {Hubert Nguyen},
publisher = {Addison-Wesley},
year = {2008},
pages = {239--256}
}