Hong Chen Ziqiang Liu Chuck Rose Yingqing Xu Heung-Yeung Shum David Salesin Example-based composite sketching of human portraits. 95-153 2004 conf/npar/2004 NPAR http://doi.acm.org/10.1145/987657.987673 db/conf/npar/npar2004.html#ChenLRXSS04