Benson L., Ljunghall S., Groth T., Falk H., Hvarfner A., Rastad J., Wide L., and Åkerström G. “Optimal Discrimination of Mild Hyperparathyroidism With Total Serum Calcium, Ionized Calcium and Parathyroid Hormone Measurements”. Upsala Journal of Medical Sciences, vol. 92, no. 2, Sept. 1987, pp. 147-76, doi:10.3109/03009738709178686.