Chin-Chen Chang Jun-Chou Chuang Yu-Chen Hu Spatial Domain Image Hiding Scheme Using Pixel-Values Differencing. 171-184 2006 70 Fundam. Inform. 3 http://iospress.metapress.com/openurl.asp?genre=article&issn=0169-2968&volume=70&issue=3&spage=171 db/journals/fuin/fuin70.html#ChangCH06