Francisco Abad Emilio Camahort Roberto Vivó Camera Calibration Using Two Concentric Circles. 688-696 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3211&spage=688 2004 conf/iciar/2004-2 ICIAR (1) db/conf/iciar/iciar2004-1.html#AbadCV04