@article {chen2010confidence,
	title = {Confidence intervals for the mean of a population containing many zero values under unequal-probability sampling},
	journal = {Canadian Journal of Statistics},
	volume = {38},
	number = {4},
	year = {2010},
	pages = {582{\textendash}597},
	publisher = {John Wiley \& Sons, Inc.},
	author = {Chen, Hanfeng and Chen, Jiahua and Chen, Shun-Yi}
}
