Dr. Liqiang Nie received a B.E. degree from Xi'an Jiaotong University of China, Xi'an, in 2009, and a Ph.D. degree from National University of Singapore, in 2013. Currently, he is a research fellow at the National University of Singapore. His research interests include social network analysis and media search. Various parts of his work have been published in top forums including ACM SIGIR, ACM MM, IJCAI, TOIS, TIST, and TMM. He served as the guest editor and special session chair for several journals and conferences, respectively.Xuemeng Song is currently a Ph.D. student at the School of Computing, National University of Singapore. She received her degree from the University of Science and Technology of China in 2012. Her research interests are information retrieval and social network analysis. She has published several papers in top venues, such as SIGIR and TOIS. In addition, she has served as a reviewer for many top conferences and journals.Dr. Chua is the KITHCT Chair Professor at the School of Co mputing, National University of Singapore. He was the Acting and Founding Dean of the School during 1998-2000. Dr. Chua's main research interest is in multimedia information retrieval and social media analysis. In particular, his research focuses on the extraction, retrieval and question-answering (QA) of text, video, and live media arising from the Web and social networks. He is the director of a multi-million-dollar joint center (named NExT) between NUS and Tsinghua University in China to develop technologies for live media search. The project will gather, mine, search, and organize user-generated content within the cities of Beijing and Singapore. His group participates regularly in TREC-QA and TRECVID video retrieval evaluations. Dr. Chua is active in the international research community. He has organized and served as program committee member of numerous international conferences in the areas of computer graphics, multimedia, and text processing. He is the conference co-chair of ACM Multimedia 2005, ACM CIVR 2005, and ACM SIGIR 2008. He serves on the editorial boards of: ACMTransactions of Information Systems (ACM), Foundationand Trends in Information Retrieval (NOW), The Visual Computer (Springer Verlag), and Multimedia Tools and Applications (Kluwer). He is a member of the steering committee of ICMR (International Conference on Multimedia Retrieval) and Multimedia Modeling conference series and a member of the international review panel of two large-scale research projects in Europe. Dr. Chua serves as the Chairman of the Board of Examiners for the Certified IT Project Management (""CITPM"") in Singapore. He is the independent Director of two publicly listed companies in Singapore. He holds a Ph.D. from the University of Leeds, UK.

• Acknowledgments.- Introduction.- Data Gathering and Completion.- Multi-source Mono-task Learning.- Mono-source Multi-task Learning.- Multi-source Multi-task Learning.- Multi-source Multi-task Learning with Feature Selection.- Research Frontiers.- Bibliography.- Authors' Biographies .

Dr. Liqiang Nie received a B.E. degree from Xi'an Jiaotong University of China, Xi'an, in 2009, and a Ph.D. degree from National University of Singapore, in 2013. Currently, he is a research fellow at the National University of Singapore. His research interests include social network analysis and media search. Various parts of his work have been published in top forums including ACM SIGIR, ACM MM, IJCAI, TOIS, TIST, and TMM. He served as the guest editor and special session chair for several journals and conferences, respectively.Xuemeng Song is currently a Ph.D. student at the School of Computing, National University of Singapore. She received her degree from the University of Science and Technology of China in 2012. Her research interests are information retrieval and social network analysis. She has published several papers in top venues, such as SIGIR and TOIS. In addition, she has served as a reviewer for many top conferences and journals.Dr. Chua is the KITHCT Chair Professor at the School of Co mputing, National University of Singapore. He was the Acting and Founding Dean of the School during 1998-2000. Dr. Chua's main research interest is in multimedia information retrieval and social media analysis. In particular, his research focuses on the extraction, retrieval and question-answering (QA) of text, video, and live media arising from the Web and social networks. He is the director of a multi-million-dollar joint center (named NExT) between NUS and Tsinghua University in China to develop technologies for live media search. The project will gather, mine, search, and organize user-generated content within the cities of Beijing and Singapore. His group participates regularly in TREC-QA and TRECVID video retrieval evaluations. Dr. Chua is active in the international research community. He has organized and served as program committee member of numerous international conferences in the areas of computer graphics, multimedia, and text processing. He is the conference co-chair of ACM Multimedia 2005, ACM CIVR 2005, and ACM SIGIR 2008. He serves on the editorial boards of: ACMTransactions of Information Systems (ACM), Foundationand Trends in Information Retrieval (NOW), The Visual Computer (Springer Verlag), and Multimedia Tools and Applications (Kluwer). He is a member of the steering committee of ICMR (International Conference on Multimedia Retrieval) and Multimedia Modeling conference series and a member of the international review panel of two large-scale research projects in Europe. Dr. Chua serves as the Chairman of the Board of Examiners for the Certified IT Project Management (""CITPM"") in Singapore. He is the independent Director of two publicly listed companies in Singapore. He holds a Ph.D. from the University of Leeds, UK.

• Acknowledgments.- Introduction.- Data Gathering and Completion.- Multi-source Mono-task Learning.- Mono-source Multi-task Learning.- Multi-source Multi-task Learning.- Multi-source Multi-task Learning with Feature Selection.- Research Frontiers.- Bibliography.- Authors' Biographies .

Dr. Liqiang Nie received a B.E. degree from Xi'an Jiaotong University of China, Xi'an, in 2009, and a Ph.D. degree from National University of Singapore, in 2013. Currently, he is a research fellow at the National University of Singapore. His research interests include social network analysis and media search. Various parts of his work have been published in top forums including ACM SIGIR, ACM MM, IJCAI, TOIS, TIST, and TMM. He served as the guest editor and special session chair for several journals and conferences, respectively.Xuemeng Song is currently a Ph.D. student at the School of Computing, National University of Singapore. She received her degree from the University of Science and Technology of China in 2012. Her research interests are information retrieval and social network analysis. She has published several papers in top venues, such as SIGIR and TOIS. In addition, she has served as a reviewer for many top conferences and journals.Dr. Chua is the KITHCT Chair Professor at the School of Co mputing, National University of Singapore. He was the Acting and Founding Dean of the School during 1998-2000. Dr. Chua's main research interest is in multimedia information retrieval and social media analysis. In particular, his research focuses on the extraction, retrieval and question-answering (QA) of text, video, and live media arising from the Web and social networks. He is the director of a multi-million-dollar joint center (named NExT) between NUS and Tsinghua University in China to develop technologies for live media search. The project will gather, mine, search, and organize user-generated content within the cities of Beijing and Singapore. His group participates regularly in TREC-QA and TRECVID video retrieval evaluations. Dr. Chua is active in the international research community. He has organized and served as program committee member of numerous international conferences in the areas of computer graphics, multimedia, and text processing. He is the conference co-chair of ACM Multimedia 2005, ACM CIVR 2005, and ACM SIGIR 2008. He serves on the editorial boards of: ACMTransactions of Information Systems (ACM), Foundationand Trends in Information Retrieval (NOW), The Visual Computer (Springer Verlag), and Multimedia Tools and Applications (Kluwer). He is a member of the steering committee of ICMR (International Conference on Multimedia Retrieval) and Multimedia Modeling conference series and a member of the international review panel of two large-scale research projects in Europe. Dr. Chua serves as the Chairman of the Board of Examiners for the Certified IT Project Management (""CITPM"") in Singapore. He is the independent Director of two publicly listed companies in Singapore. He holds a Ph.D. from the University of Leeds, UK.

• Acknowledgments.- Introduction.- Data Gathering and Completion.- Multi-source Mono-task Learning.- Mono-source Multi-task Learning.- Multi-source Multi-task Learning.- Multi-source Multi-task Learning with Feature Selection.- Research Frontiers.- Bibliography.- Authors' Biographies .