@article {crainiceanu2009nonparametric, title = {Nonparametric signal extraction and measurement error in the analysis of electroencephalographic activity during sleep}, journal = {Journal of the American Statistical Association, PMCID: PMC2802498}, volume = {104}, number = {486}, year = {2009}, pages = {541{\textendash}555}, publisher = {ASA}, author = {Crainiceanu, C and Caffo, B and Di, C and Punjabi, N} }