http://exam.freepatentbar.com/chalkboard/april-2000-am/34
http://exam.freepatentbar.com/chalkboard/october-2002-am/34
http://exam.freepatentbar.com/chalkboard/october-2003-am/34
http://exam.freepatentbar.com/chalkboard/october-2003-pm/34
