Recommended by ADAC: https://www.adac.de/infotestrat/reparatur-pflege-und-wartung/motor-und-oel/motoroel/default.aspx?ComponentId=27479&SourcePageId=49407
F. Suchanek, G. Kasneci, and G. Weikum. Proceedings of the 16th International Conference on World Wide Web, page 697--706. New York, NY, USA, ACM, (2007)
S. Liu, C. Yu, and W. Meng. Proceedings of the 14th ACM International Conference on Information and Knowledge Management, page 525--532. New York, NY, USA, ACM, (2005)