There is also a discussion of this "level system" of complexities on Lipton and Regan's blog https://rjlipton.wordpress.com/2017/01/04/babais-result-still-a-bre

There is also a discussion of this "level system" of complexities on Lipton and Regan's blog https://rjlipton.wordpress.com/2017/01/04/babais-result-still-a-breakthrough/ https://rjlipton.wordpress.com/2017/01/04/babais-result-stil...