H. Wang, J. J. Zhang, S. Z. Li, and Y. Wang, “Shape and texture preserving non-photorealistic rendering,” Comput. Animation Virtual World, vol.15, no.3/4, pp. 453-461, 2004.
B. Gooch, E. Reinhard, and A. Gooch, “Human facial illustrations: Creation and psychological evaluation,” ACM Trans. Graphics, vol.23, no.1, pp. 27-44.2004.