Please when referencing the Stack-Of-Tasks use the following reference:
"A versatile Generalized Inverted Kinematics implementation for collaborative working humanoid robots: The Stack Of Tasks" , N. Mansard, O. Stasse, P. Evrard, A. Kheddar, Int. Conf. on Autonomous Robots, ICAR, 2009
"Task sequencing for sensor-based control", N. Mansard, F. Chaumette, IEEE Trans. on Robotics, 23(1):60-72, February 2007