Guo Guizhi worked in The Chinese National Railway Company and in this way he was naturally inclined to study first Yiquan with Dr. Yu Yongnian who was working at that time in the Chinese Railway Hospital, later he studied also with Yao Zongxun. Guo is among the first Chinese Yiquan experts to come in Europe to introduce this art and still figures there as a reference. He had always a reputation of fighter and we can still feel it here in the martial application through is now 74.
For about Guo Guizhi’s theoretical background: read his master Dr. Yu Yongnian’s articles:
http://yiquan.chinamartialarts.net/yu.htm
But also the famous ebook “Zhan zhuang and the Search of Wu”:
http://yiquan.chinamartialarts.net/Yu-YN-ebook.html