@book{579,
	author = {Oppenheim, Alan V., and Willsky, Alan S.},
	title = {Signals & Systems.},
	publisher = {Pearsdon,},
	year = {1997.},
	address = {New Delhi :},
	edition = {2nd ed.},
	url = {https://www.amazon.com/Signals-Systems-2nd-Alan-Oppenheim/dp/0138147574/ref=sr_1_2?keywords=9780138147570&linkCode=qs&qid=1640582219&s=books&sr=1-2}
}