@article {helal2013variational,
	title = {Variational principle for Zakharov{\textendash}Shabat equations in two-dimensions},
	journal = {Applied Mathematics and Computation},
	volume = {219},
	number = {10},
	year = {2013},
	note = {n/a},
	pages = {5635{\textendash}5648},
	publisher = {Elsevier},
	abstract = {n/a},
	author = {M. A. Helal and Aly R. Seadawy and Ibrahim, RS}
}
