http://exam.freepatentbar.com/chalkboard/october-2000-am/2
http://exam.freepatentbar.com/chalkboard/october-2002-am/2
http://exam.freepatentbar.com/chalkboard/april-2003-am/2
http://exam.freepatentbar.com/chalkboard/october-2003-pm/2
