Motilal Agrawal Larry S. Davis Camera calibration using spheres: A semi-definite programming approach. 782-791 2003 conf/iccv/2003 ICCV http://csdl.computer.org/comp/proceedings/iccv/2003/1950/02/195020782abs.htm db/conf/iccv/iccv2003-2.html#AgrawalD03