Identifying quasars with astrometric and mid-infrared methods from APOP and ALLWISE Sufen Guo, Zhaoxiang Qi, Shilong Liao, Zihuang Cao, Mario G. Lattanzi, Beatrice Bucciarelli, Zhenghong Tang and Qing-Zeng Yan A&A, 618 (2018) A144 Published online: 24 October 2018 DOI: 10.1051/0004-6361/201833135