@conference {539,
	title = {DS4: Introducing Semantic Friendship in Distributed Social Networks.},
	booktitle = {Proceedings of the 21st International Conference on Cooperative Information Systems (CoopIS)},
	year = {2013},
	month = {September},
	address = {Graz, Austria},
	author = {Paraskevi Raftopoulou and Christos Tryfonopoulos and E.G.M. Petrakis and Nikos Zevlis}
}
