Sleep-wake differences in scaling behavior of the human heartbeat: Analysis of terrestrial and long-term space flight dataP. Ch. Ivanov, A. Bunde, L. A.N. Amaral, S. Havlin, J. Fritsch-Yelle, R. M. Baevsky, H. E. Stanley and A. L. GoldbergerEurophys. Lett., 48 5 (1999) 594-600DOI: https://doi.org/10.1209/epl/i1999-00525-0