@book{50381,
	author = {Marshall, Alfred},
	title = {Elements of economics of industry /},
	publisher = {Macmillan,},
	year = {1907.},
	address = {London :},
	edition = {Fourth Edition},
	note = {Includes index.},
	url = {https://fll.law.cu.edu.eg/fulltext/bks/B13-08431.pdf}
}