@ARTICLE {26640,
author={L.  Li and P.L. Correia and A.H. Hadid},
doi={10.1049/iet-bmt.2017.0089},
journal={IET Biometrics},
title={         Face recognition under spoofing attacks: countermeasures and research directions      },
year={2018},
month={January},
volume={7},
number={1},
pages={3-14},
ISSN={2047-4938}
}