1. Graduate School of Informatics and Engineering, The University of Electro-Communications, Tokyo 182-8585, Japan
2. Inner Mongolia University of Finance and Economics Library, Inner Mongolia University of Finance and Economics, Hohhot 010051, China
3. B & S Tech Co., Ltd., Arakawa-ku, Tokyo 116-0014, Japan
4. School of Computer Science and Information Engineering, Hohhot Minzu College, Hohhot 010051, China