@book{4048,
	author = {Kotonya, Gerald and Sommervile,Ian},
	title = {Requirements Engineering .},
	publisher = {John wiley & sons,},
	year = {2003},
	address = {Chichester :},
	url = {https://books.google.com.pk/books/about/Requirements_Engineering.html?id=Up1QAAAAMAAJ&source=kp_book_description&redir_esc=y}
}