Coxeter, H. S. M. (1991), «Orthogonal trees», en Drysdale, Robert L. Scot, ed., Proceedings of the Seventh Annual Symposium on Computational Geometry, North Conway, NH, USA, June 10–12, 1991, Association for Computing Machinery, pp. 89-97, S2CID18687383, doi:10.1145/109648.109658.
Coxeter, H. S. M. (1991), «Orthogonal trees», en Drysdale, Robert L. Scot, ed., Proceedings of the Seventh Annual Symposium on Computational Geometry, North Conway, NH, USA, June 10–12, 1991, Association for Computing Machinery, pp. 89-97, S2CID18687383, doi:10.1145/109648.109658.