Tim Salzman Szymon Stachniak Wolfgang Stürzlinger Unconstrained vs. Constrained 3D Scene Manipulation. 207-220 2001 conf/ehci/2001 EHCI http://link.springer.de/link/service/series/0558/bibs/2254/22540207.htm db/conf/ehci/ehci2001.html#SalzmanSS01