Hofmann, M., C. Gatu, E. J. Kontoghiorghes, A. Colubi, and A. Zeileis. “LmSubsets: Exact Variable-Subset Selection in Linear Regression for R”. Journal of Statistical Software, vol. 93, no. 3, Apr. 2020, pp. 1-21, doi:10.18637/jss.v093.i03.