Pickle, Linda Williams, James B. Pearson, and Daniel B. Carr. “MicromapST: Exploring and Communicating Geospatial Patterns in US State Data”. Journal of Statistical Software 63, no. 3 (February 10, 2015): 1–25. Accessed August 18, 2022. https://www.jstatsoft.org/index.php/jss/article/view/v063i03.