Alexander S. Szalay Jim Gray George Fekete Peter Z. Kunszt Peter Kukol Ani Thakar Indexing the Sphere with the Hierarchical Triangular Mesh http://arxiv.org/abs/cs/0701164 2007 CoRR abs/cs/0701164 db/journals/corr/corr0701.html#abs-cs-0701164 informal publication