I recently stumbled across this website, by a Go enthusiast named Harry Fearnley
A lot of interesting content about seki (including hanezeki and nakade) and “beasts” (peculiar positions that are difficult to understand and potentially challenge various rule sets).
This is a bit like an Antarctica of Go for me!
A beautiful and vital place that makes the world the beautiful place that it is, and I’m glad that it is there, but I can’t see myself going there because it is too challenging 
You might also be interested in Richard Hunters series of articles also in the British Go Journal. He republish the articles in book form as The monkey jump workshop, cross cut workshop and Counting Liberties and capturing races.
Specifically the last one I mean, apparently they’re found in issues 102 to 120, so you’d have to look through them (not too bad they have tables of contents and things) just to see which ones are the capturing race ones.
The book is fairly cool, lots of discussion of when groups in capturing races end in seki.