Lilei Zheng Khalid Idrissi Christophe Garcia Stefan Duffner Atilla Baskurt Triangular similarity metric learning for face verification. 1-7 2015 FG https://doi.org/10.1109/FG.2015.7163085 https://doi.ieeecomputersociety.org/10.1109/FG.2015.7163085 conf/fgr/2015 db/conf/fgr/fg2015.html#ZhengIGDB15