Jolbäck, Per, et al. “A Small Number of Surgeons Outside the Control-Limit: An Observa- Tional Study Based on 9,482 Cases and 208 Surgeons Performing Primary Total Hip Arthroplasties in Western Sweden”. Acta Orthopaedica, vol. 91, no. 5, June 2020, pp. 581–586, doi:10.1080/17453674.2020.1772584.