C. Schuldt, I. Laptev, and B. Caputo. Pattern Recognition, 2004. ICPR 2004. Proceedings of the 17th International Conference on, 3, page 32--36. IEEE, (2004)
M. Lux, M. Granitzer, and R. Kern. Database and Expert Systems Applications, 2007. DEXA'07. 18th International Workshop on, page 283--287. IEEE, (2007)