Ryan Schmidt Tobias Isenberg Pauline Jepp Karan Singh Brian Wyvill Sketching, Scaffolding, and Inking: A Visual History for Interactive 3D Modeling. 23-32 2007 conf/npar/2007 NPAR http://doi.acm.org/10.1145/1274871.1274875 db/conf/npar/npar2007.html#SchmidtIJSW07