W. Kangchareonsombat, P. Villacuna, V. G Bird, C. M Lynne, and R. J Leveillec, “Upper Pole versus Lower Pole Access for Percutaneous Nephrolithotomy (PCNL) in Patients with Multiple Renal Calculi”, Vajira Med J, vol. 50, no. 1, pp. 21–25, Sep. 2011.