MacDonald, Blake, Pritam Ranjan, and Hugh Chipman. “GPfit: An R Package for Fitting a Gaussian Process Model to Deterministic Simulator Outputs”. Journal of Statistical Software 64, no. 12 (April 8, 2015): 1–23. Accessed May 26, 2022. https://www.jstatsoft.org/index.php/jss/article/view/v064i12.