“…Canonical correlation analysis (CCA) [16] and co-training [17] are always viewed as the early work of multi-view learning, and scholars have used them as a basis to develop many variants in this field. According to Sun's book [18] (the first book on multi-view learning), the research topics in this area mainly include: multiview supervised [19,20] and semi-supervised [21,22] learning, multi-view subspace learning [23,24], multi-view clustering [25,26,27], multi-view active learning [28,29], multi-view transfer [30] and multi-task learning [31,9], multi-view deep learning [32], and view construction [33]. Besides, the field can be widely used in plenty of applications, such as computer vision [34], social network [35], recommendation Systems [36], and medical research [37].…”