@book{1159,
	author = {Date, C. J. and Swamynathan,S},
	title = { An Introduction to Database Systems.},
	publisher = {Pearson,},
	year = {2006.},
	address = {Boston :},
	edition = {8th ed.},
	url = {https://books.google.com.pk/books/about/An_Introduction_to_Database_Systems.html?id=2xBRAAAAMAAJ&source=kp_book_description&redir_esc=y}
}