Ingmar Seeliger Ulrich Schwanecke Peter Barth An Optical Pen Tracking System as Alternative Pointing Device. 386-399 2009 INTERACT (2) http://dx.doi.org/10.1007/978-3-642-03658-3_44 conf/interact/2009-2 db/conf/interact/interact2009-2.html#SeeligerSB09