Toshiyuki Okamura Buntarou Shizuki Jiro Tanaka Execution Visualization and Debugging in Three-Dimensional Visual Programmin. 167-172 2004 conf/iv/2004 IV http://csdl.computer.org/comp/proceedings/iv/2004/2177/00/21770167abs.htm db/conf/iv/iv2004.html#OkamuraST04