Alexander Zelinsky Yoshio Matsumoto Jochen Heinzmann Rhys Newman Towards Human Friendly Robots: Vision-based Interfaces and Safe Mechanisms. 487-498 1999 conf/iser/1999 ISER db/conf/iser/iser1999.html#ZelinskyMHN99 https://doi.org/10.1007/BFb0119426