Frank Drewes Annegret Habel Hans-Jörg Kreowski Stefan Taubenberger Generating Self-Affine Fractals by Collage Grammars. 159-187 1995 145 Theor. Comput. Sci. 1&2 db/journals/tcs/tcs145.html#DrewesHKT95 http://dx.doi.org/10.1016/0304-3975(94)00118-3