@article{journals/tods/OzsoyogluOM87,
	title = {Extending Relational Algebra and Relational Calculus with Set-Valued Attributes and Aggregate Functions.},
	author = {Gultekin Özsoyoglu and Z. Meral Özsoyoglu and Victor Matos},
	journal = {ACM Trans. Database Syst.},
	number = {4},
	pages = {566-592},
	url = {http://dblp.uni-trier.de/db/journals/tods/tods12.html#OzsoyogluOM87},
	volume = {12},
	year = {1987},
	biburl = {http://www.bibsonomy.org/bibtex/2f0be8fe287119ee48c54de35375fc2be/schmitz},
	description = {dblp},
	ee = {db/journals/tods/OzsoyogluOM87.html}, date = {2006-04-03}, cite = {...}, cdrom = {TODS12/P566.PDF},
	keywords = {algebra database folksonomy relational }
}