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.

A Low-Cost Positioning System for Location-Aware Applications in Smart Homes
R. Schäfer, W. Müller, R. Deimann, B. Kleinjohann, in: Proceedings of the Workshop on Mobile Spatial Interaction at CHI 2007, San Jose, USA, 2007.