Prospective randomized comparison of transumbilical two-port laparoscopic and conventional laparoscopic varicocele ligation oleh Guo-Xi Zhang, Jun Yang, Da-Zhi Long, Min Liu, Xiao-Feng Zou, Yuan-Hu Yuan, Ri-Hai Xiao, Yi-Jun Xue, Xin Zhong, Quan-Liang Liu, Fo-Lin Liu, Bo Jiang, Rui-Quan Xu, Kun-Lin Xie