Aaron Greenfield Uluc Saranli Alfred A. Rizzi Solving Models of Controlled Dynamic Planar Rigid-Body Systems with Frictional Contact. 911-931 2005 24 I. J. Robotic Res. 11 http://ijr.sagepub.com/cgi/content/abstract/24/11/911 db/journals/ijrr/ijrr24.html#GreenfieldSR05