@article {heckman_penalized_2000,
	title = {Penalized regression with model-based penalties},
	journal = {Canadian Journal of Statistics},
	volume = {28},
	number = {2},
	year = {2000},
	pages = {241{\textendash}258},
	url = {http://onlinelibrary.wiley.com/doi/10.2307/3315976/abstract},
	author = {Heckman, Nancy E. and Ramsay, James O.}
}
