A. Avrunin, R. Tikhilov, I. Shoubniakov, D. Pliev, V. Popov, and V. Emelyanov, “A minimum required number of studies of PBMD by DERA method in individual diagnosis of oteoporosis and monitoring of the skeleton state by the distal forearm”, OTP, no. 1, pp. 49–56, Aug. 2009.