@inproceedings{RecSys-2011-SparlingS,
	author        = "E. Isaac Sparling and Shilad Sen",
	booktitle     = "{Proceedings of the Fifth Conference on Recommender Systems}",
	doi           = "10.1145/2043932.2043961",
	isbn          = "978-1-4503-0683-6",
	pages         = "149--156",
	publisher     = "{ACM}",
	title         = "{Rating: how difficult is it?}",
	year          = 2011,
}