@book{7036,
	author = {Drooyan, Irving. and Hadel, Walter,},
	title = {Essentials of trigonometry /},
	publisher = {Macmillan,},
	year = {c1977.},
	address = {New York :},
	edition = {2d ed.},
	note = {"A portion of this material has been adapted from Trigonometry: an analytical approach."}
}