@article {caffo2009overview,
	title = {An overview of observational sleep research with application to sleep stage transitioning},
	journal = {Chance, PMCID: PMC2800358},
	volume = {22},
	number = {1},
	year = {2009},
	pages = {10{\textendash}15},
	publisher = {Springer},
	author = {Caffo, B and Swihart, B and Crainiceanu, C and Laffan, A and Punjabi, N}
}
