Short-term simulation training course improves basic obstetric ultrasound operational skills of residents: A multi-center study - Yongfeng Zhao; Ping Zhou; Xiaohong Tang; Wenhui Zhu; Wengang Liu; Jinguang Zhou; Jie Wang; Yingchun Luo; Junhui Zhang; Lan Yang; Yan Xu (PLoS ONE, 2025)