@article {litwin2011social,
	title = {Social network type and subjective well-being in a national sample of older Americans},
	journal = {The Gerontologist},
	volume = {51},
	number = {3},
	year = {2011},
	pages = {379{\textendash}388},
	publisher = {Oxford University Press},
	author = {Litwin, Howard and Shiovitz-Ezra, Sharon}
}
