Tamai, Kazuya, et al. “HLA-B27-Negative Ankylosing Spondylitis Resulting in Panclavicular Ligament ossification–a 28-Year Follow-up”. Acta Orthopaedica, vol. 69, no. 3, Jan. 1998, pp. 323-5, doi:10.3109/17453679809000941.