SURF was first presented at the ECCV 2006 conference in Graz (Austria). Please reference the CVIU journal version:

Herbert Bay, Andreas Ess, Tinne Tuytelaars, Luc Van Gool, "SURF: Speeded Up Robust Features", Computer Vision and Image Understanding (CVIU), Vol. 110, No. 3, pp. 346--359, 2008
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