@conference {875,
	title = {Social Comparisons to Motivate Contributions to an Online Community.},
	booktitle = {Persuasive Technology},
	year = {2007},
	month = {26/04/2007},
	address = {Palo Alto, CA},
	author = {F. Harper and X. Li and Y. Chen and J. Konstan}
}
@conference {902,
	title = {An Economic Model of User Rating in an Online Recommender System},
	booktitle = {10th International Conference on User Modeling},
	year = {2005},
	address = {Edinburgh, UK},
	author = {F.M. Harper and X. Li and Y. Chen and Konstan, J.A.}
}
