@article{Li2009,
author = {Li, Hongbin and Zheng, Hui},
title= {Ultrasonography and sex ratios in China},
year = {2009},
doi = {10.1111/j.1748-3131.2009.01115.x},
URL = {https://doi.org/10.1111/j.1748-3131.2009.01115.x},
volume = {4},
number = {1},
pages = {121--137},
}