Parameter estimation and classification of censored Gaussian data with application to WiFi indoor positioning
M.K. Hoang, R. Haeb-Umbach, in: 38th International Conference on Acoustics, Speech, and Signal Processing (ICASSP 2013), 2013, pp. 3721–3725.

Parameter Estimation of a State-Space Model of Noise for Robust Speech Recognition
S. Windmann, R. Haeb-Umbach, IEEE Transactions on Audio, Speech, and Language Processing 17 (2009) 1577–1590.