I've been reading about BBDs and clocks recently and I ran across this research paper. I wish more universities had a guitar FX department!
https://ant-s4.unibw-hamburg.de/dafx/paper-archive/2016/dafxpapers/14-DAFx-16_paper_59-PN.pdf
Very interesting considering that it was published in 2016, and bbds are from the 60's. There are some more hidden papers and patents too.