P. van der Merwe and E. Grobbelaar, “Stability of 19-norandrosterone and 19-noretiocholanolone glucuronide in urine under various storage conditions”, SA J Sports Med, vol. 15, no. 2, pp. 14–17, Dec. 2003, doi: 10.17159/2078-516X/2003/v15i2a217.