@article {4007,
	title = {Implication Problems for Functional Constraints on Databases Supporting Complex Objects},
	journal = {Journal of Computer and System Sciences (JCSS)},
	volume = {49},
	year = {1994},
	pages = {726--768},
	doi = {10.1016/S0022-0000(05)80078-9},
	author = {Minoru Ito and Grant Weddell}
}
