[1] 2017 U.S. Cement Industry Annual Yearbook, Portland Cement Association

[2] Clean Air Act, 42 U.S.C. §7401 et seq. (1970), sections 112 and 129

[3] U.S. Environmental Protection Agency, Frequent Questions about the Identification of Non-hazardous Secondary Materials that are Solid Wastes https://www.epa.gov/rcra/frequent-questions-about-identification-non-hazardous-secondary-materials-are-solid-wastes

[4] 2016 U.S. Labor-Energy Input Survey, Portland Cement Association