@article {36613,
	title = {Sightability adjustment methods for aerial surveys of wildlife populations},
	volume = {45},
	year = {1989},
	pages = {415-425},
	publisher = {Biometrics},
	url = {http://www.jstor.org/stable/2531486?seq=1},
	author = {Steinhorst, R. Kirk and Samuel, Michael D.}
}
