1. Abel, D.J., J.L. Smith (1983): A data structure and algorithm based on a linear key for a rectangle retrieval problem; Computer Vision, Graphics, and Image Processing, Vol. 24, 1–13
2. Abel, D.J., D.M. Mark (1990): A comparative analysis of some two-dimensional orderings; Intern. J. of Geographical Information Systems, Vol. 4, No. 1, 21–31
3. Asano, T., A. Hasegawa, D. Ranjan, T. Roos (1993): Optimal and Approximate Digital Halftoning Algorithms and their Experimental Evaluation, Extended Abstract, Proc. Asian Conference on Computer Vision ACCV'93, Osaka
4. Asano, T., A. Hasegawa, D. Ranjan, T. Roos (1994): Optimal and Approximate Digital Halftoning Algorithms and their Experimental Evaluation, submitted
5. Bugnion, E., T. Roos, P. Widmayer (1994): Indexing Points with Space Filling Curves, private communications