@article {9518,
	title = {Comparison of statistical approaches for dealing with immortal time bias in drug effectiveness studies},
	journal = {American Journal of Epidemiology},
	volume = {184},
	year = {2016},
	pages = {857-858},
	type = {Letter},
	author = {Karim, M.E. and Gustafson, P. and Petkau, J. and Tremlett, T.}
}
