Azeez, Ali Abid Hussan, and Rehab Flaih Hassan. “Using Space-Filling Curves to Improve the Quad Tree for Spatial Indexing”. Journal of Al-Qadisiyah for Computer Science and Mathematics, vol. 11, no. 3, Sept. 2019, pp. Comp Page 94-104, doi:10.29304/jqcm.2019.11.3.610.