Itsuo Kumazawa Evaluation of User-Friendliness of a Compact Input Device with Simple Tactile Feedback. 121-127 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3031&spage=121 2004 conf/sg/2004 Smart Graphics db/conf/sg/sg2004.html#Kumazawa04