Reduced Sleep Duration and Sleep Efficiency Were Independently Associated With Frequent Nightmares in Chinese Frontline Medical Workers During the Coronavirus Disease 2019 Outbreak oleh Yi-Qi Lin, Ze-Xin Lin, Yong-Xi Wu, Lin Wang, Lin Wang, Zhao-Nan Zeng, Zhao-Nan Zeng, Qiu-Yang Chen, Qiu-Yang Chen, Ling Wang, Ling Wang, Xiao-Liang Xie, Xiao-Liang Xie, Shi-Chao Wei