@book{13890,
	author = {Gamma, Erich ; Helm, Richard ; Johnson, Ralph ; Vlissides, John},
	title = {Design Patterns: Elements of reusable object-oriented software},
	publisher = {Pearson Education Inc},
	year = {,2017.},
	address = {Uttar Pradesh:},
	edition = {NA},
	note = {Includes Index}
}