(2) N. Ravi, N. Dandekar, P. Mysore, and M.L. Littman. Activity recognition from accelerometer data. In IAAI 2005, volume 20, pages 1541-1546, 2005.
(3) A.P. Dempster, N.M. Laird, D.B. Rubin, et al. Maximum likelihood from incomplete data via the em algorithm. Journal of the Royal Statistical Society. Series B (Methodological), 39(1):1-38, 1977.