1. Web Sciences Center, University of Electronic Science and Technology of China, Chengdu 610054, China
2. Big Data Research Center, University of Electronic Science and Technology of China, Chengdu 610054, China
3. Department of Engineering Mathematics, University of Bristol, Bristol BS8 1UB, United Kingdom
4. Centre for Networks and Collective Behaviour, Department of Mathematical Sciences, University of Bath, Claverton Down, BA2 7AY Bath, United Kingdom