Any good Books or Articles on Hei Cha?

Hi everyone, I am new to this forum, and learned a lot from your posts.

I did a lot of search, hoping to find some Hei Cha books/ articles written in English, but could find nothing except for a few posts in tea forums/blogs.

Do you have any recommendation on the topic, or related topics?

Charlie mentioned in one post he draws the difference between Heicha and others in his book. Is it a book about Hei Cha? I am really looking forward to reading it.  Could anyone let me know the name of the book?  Many thanks!