1. Chang Gung University of Science and Technology, Tao-Yuan, Taiwan; and Chang Gung Memorial Hospital, Tao-Yuan, Taiwan
2. Pui Ching Middle School, Hong Kong; and Queen’s College, Taunton, Somerset, United Kingdom
3. Department of Mathematics, Tsinghua University, Beijing, China
4. Yau Mathematical Sciences Center, Tsinghua University, Beijing, China