Meng Xiao Hong Yan Xianglin Yang Yanjun Li Ruiyun Zhu Multiscale entropy based analysis of HRV during sleep. 558-562 2012 BMEI https://doi.org/10.1109/BMEI.2012.6512919 conf/bmei/2012 db/conf/bmei/bmei2012.html#XiaoYYLZ12