Author,Title,Journal,ISSN,Publisher,Date,Volume,Number,Page,URL,URL(DOI) FUJIWARA Yoshihisa and KURODA Shohei and OKADA Shima and MATSUURA Hidefumi and YASUDA Masashi and IIDA Takeo and MAKIKAWA Masaaki,Estimation of Sleep Stage from Heart Rate Variability Using Chaos Analysis,Transactions of Japanese Society for Medical and Biological Engineering,1347443X,Japanese Society for Medical and Biological Engineering,2003,41,4,328-334,https://cir.nii.ac.jp/crid/1390282680243168640,https://doi.org/10.11239/jsmbe2002.41.328