Xie Yanting (right) introduces his research on graph theory to his teachers and classmates in a class at Lanzhou University in Gansu province. CHINA DAILY

From undergraduate to PhD, Lanzhou student has published three theses and is preparing to defend the latest

Though physically challenged, 31-year-old Xie Yanting, who has cerebral palsy, does not inhabit a small world.

He has been auditing courses at Lanzhou University in Gansu province for the last 12 years, and he recently submitted his doctoral thesis.

The years of study, which have taken Xie from undergraduate to postgraduate and now doctorate, have not been easy, but for both Xie and his mother, it has been a happy time filled with love and encouragement.

One day in March, he left at 7 am to audit a class at the School of Mathematics and Statistics as usual. In fact, even when he doesn't have a class, Xie still goes to school to study alone or read in the library.

He doesn't talk much, mainly because he's unable to speak clearly, but when he gets onto the subject of graph theory, the branch of mathematics he is studying, Xie becomes quite chatty.

"I particularly like all the graphs," he said.

For Xie, mathematics is not just work and study, it's also a hobby and an interest.

"When I lie in bed at night, math graphs come to mind. They are so clear and so beautiful," he said.

Xie has three theses listed in the Science Citation Index (SCI), a world-leading thesis index system, all written in English.

He's only able to type with one finger, and he's spent countless nights typing his thoughts and research into the computer, but he finds it a pleasure because he is deeply immersed in his studies.

He has also submitted a thesis to the Journal of Graph Theory and is waiting to hear whether it will be accepted. This is his second attempt to get published in the internationally renowned journal. He submitted his thesis for the first time in March last year but was turned down.

"I've revised it and added some content and submitted it again. It's a learning process, one that I cherish," Xie said.

His mother, Liu Xiaofeng, said, "Mathematics has not only enriched his life, but has given him a way to integrate with society."

Before he began auditing classes in 2011, Xie had spent the previous 19 years at home, mostly with his mother and grandfather.

He cherishes time on campus so much that he not only took every course he could, but also attended most of the class activities.

"I have felt happiest over the years at Lanzhou University. I have made a lot of friends and we have discussed our studies together, and I have taken part in a lot of activities, including mountain climbing," he said.

Xie's graduation photo stands on the table beside his bed and is prominent in his WeChat moments, where he has posted many pictures with teachers and classmates.

"He is obsessed with math and is good at mental arithmetic," said Gao Chen, one of his friends. "He's interested in a wide range of sectors and knows a lot."

Xie also likes watching movies and singing. "When he sings in the morning or in the afternoon, I know he is happy," his mother said.

Xie was diagnosed with cerebral palsy when he was 11 months old, and Liu has been taking care of him day and night ever since. She has taken him to hospitals in big cities to see doctors, looked after his daily needs and even accompanied him to university.

Xie knows how hard it is for his mother to take care of him. In his doctoral thesis, he acknowledged her by saying: "Since my birth, my mother has been educating me like anyone else. She has done so much for me, especially after my father passed away. Mom, I love you."

He said that he is lucky to be surrounded by love and that his teacher, Xu Shoujun, and his classmates all have had a positive influence on his attitude toward life.

It is Xie's hope that people with cerebral palsy will have more opportunities to study at school, rather than being confined to their homes.

"Our lives are not as hard as people think. My son is happy, and so am I," Liu said.