@incollection{ref,
author = {Bert Freudenberg and Maic Masuch and Thomas Strothotte},
title = {Real-Time Halftoning: Fast and Simple Stylized Shading},
booktitle = {Game Programming Gems 4},
editor = {Andrew Kirmse},
publisher = {Charles River Media},
year = {2004},
pages = {443--449}
}