20. 1. G. Oriolo, Control of Nonholonomic Systems, Lecture Notes,
http://www.dis.uniroma1.it/~oriolo/cns/cns_slides.pdf
2. M. Manson, Nonholonomic Constraint, Lecture Notes,
http://www.cs.rpi.edu/~trink/Courses/RobotManipulation/lectures/lecture5.pdf
3. G. Oriolo, Wheeled Mobile Robots:Modeling, Planning and Control, 2010 SIDRA Doctoral
School on Robotics, http://bertinoro2010.dii.unisi.it