Silman, Alan J, et al. “International Variation in Distribution of ASA Class in Patients Undergoing Total Hip Arthroplasty and Its Influence on Mortality: Data from an International Consortium of Arthroplasty Registries”. Acta Orthopaedica, vol. 92, no. 3, Mar. 2021, pp. 304–310, doi:10.1080/17453674.2021.1892267.