1. Van Brussel, H., C.C. Van Helsdingen, K. Machiels, “FROG: Free Ranging on Grid. New Perspectives in Automated Transport”, Proc. AGV6, IFS/Springer, 1988.
2. Song, K.T., “Planning and Control of a Mobile Robot based on an Ultrasonic Sensor”, Ph.D. Thesis, K.U. Leuven, 1989.