1. School of Science, Institute for Artificial Intelligence, Southwest Petroleum University, Chengdu, People's Republic of China
2. Faculty of Mathematics and Computer Science, Jagiellonian University in Krakow, Krakow, Poland
3. School of Mathematics and Physics, Guangxi University for Nationalities, Nanning, People's Republic of China
4. Departement of Mathematics, FPT University, Hanoi, Vietnam