FERMI LARGE AREA TELESCOPE THIRD SOURCE CATALOG - Acero, F.; Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Belfiore, A.; Bellazzini, R.; et al. (Astrophysical Journal Supplement Series, 2015)