Kjægaard-Andersen, Per, Martin Søe Steinke, Kjeld Hougaard, Jens Ole Søjbjerg, and Jørn Jensen. 1991. “Heterotopic Bone Formation Following Hip Arthroplasty: A Retrospective Study of 65 Bilateral Cases”. Acta Orthopaedica 62 (3):223-25. https://doi.org/10.3109/17453679108993596.