At the moment I am teaching the Wenwang bagua 文王八卦 method of using the Yi at the Oriental College in Amsterdam. Here in the West it is a quite unknown way of using the Yi, probably because it is complicated and the Western literature which we have about this subject does not help much in comprehending it. Wenwang bagua uses a lot of words/terms which have to be properly described to understand them. It does not suffice to give a list of meanings for each of the liuqin 六親, you also have to describe them, otherwise your students are not able to add new material to the lists; they have not learned to expand on what they are taught. Alex Chiu does a good job at that, but since he made up his own words for certain terms (calling the liuqin 'stars') it is still not always easy to follow.
A name which pops up very often when you read Chinese books about WWBG is Ye He 野鶴, 'Wild Crane'. 'Ye He' is probably a pseudonym, because 'wild crane' is used to describe a recluse. I read somewhere that Ye He lived during the Song dynasty (960–1279). The book he wrote, Zengshan Pu Yi 增刪卜易, 'The Revised Fortunetelling Changes', is very influential and all major authors who write about WWBG quote from it.
It is not easy material, but if you want to know where Alex got his material from, and what inspired others, you surely must take a look at Ye He's book. It can be downloaded here (you first have to register). This site contains a lot of other goodies which are worth checking out.