Chanun Lewchalermvongs. (2009) A variation of the opaque problem. Mahidol University,:ม.ป.ท.Chanun Lewchalermvongs. 2009. A variation of the opaque problem. ม.ป.ท.:Mahidol University,;Chanun Lewchalermvongs. A variation of the opaque problem. ม.ป.ท.:Mahidol University, 2009. Print.