Federated Learning Meets Blockchain in Edge Computing: Opportunities and Challenges[J] IEEE INTERNET OF THINGS JOURNAL 2021(8) Nguyen, Dinh C. Ding, Ming Quoc-Viet Pham Pathirana, Pubudu N. Le, Long Bao Seneviratne, Aruna Li, Jun Niyato, Dusit Poor, H. Vincent