Akahane, Tsutomu, et al. “Serum Total Acid Phosphatase for Monitoring the Clinical Course of Giant Cell Tumors of bone—26 Patients With 5 Local Recurrences”. Acta Orthopaedica, vol. 76, no. 5, Jan. 2005, pp. 651-3, doi:10.1080/17453670510041727.