Solving RecSys Challenge 2015 by Linear Models, Gradient Boosted Trees and Metric Optimization. - Róbert Pálovics; Peter Szalai; Levente Kocsis; Adrienn Szabó; Erzsébet Frigó; Júlia Pap; Zsófia K. Nyikes; András A. Benczúr (RecSys Challenge, 2015)