@book{6133,
	author = {Polit, Denise F.},
	title = { Essentials of nursing research : methods, appraisal, and utilization},
	publisher = {Lippincott,},
	year = {1997.},
	address = {Philadelphia :},
	edition = {4th ed.},
	url = {https://books.google.com.pk/books?id=kUdIP_YJB2EC&dq=9780397553686&source=gbs_similarbooks}
}