Miller, Harvey. Tobler's First Law and Spatial Analysis. Annals of the Association of American Geographers. 2004, 94 (2): 284–289. doi:10.1111/j.1467-8306.2004.09402005.x.
Goodchild, Michael. The Validity and Usefulness of Laws in Geographic Information Science and Geography. Annals of the Association of American Geographers. 2004, 94 (2): 300–303. doi:10.1111/j.1467-8306.2004.09402008.x.