1. Laboratory of Language Engineering and Computing, Guangdong University of Foreign Studies, Guangzhou, China
2. Laboratory of Language and Artificial Intelligence, Guangdong University of Foreign Studies, Guangzhou, China
3. School of Information Science and Technology, Guangdong University of Foreign Studies, Guangzhou, China
4. School of Computer Science, Central China Normal University, Wuhan, China
5. School of Information Science and Technology, Qiong Tai Normal University, Haikou, China