I get hold of them thanks to my uni access. I couldn't afford that myself. 🤧
Problem is the demand is pretty low. I have seen my prof had a CRC monograph. Last time I checked the retail price was 110 usd. And it's still in print.
As for your comment, I don't think it's all fun for behind some benign counter examples, there have been considerate underlying research.
I typically don't enjoy extremely contrived counter examples. Luckily the one in the post is quite easily motivated so, it was on the easier side.
It reminds me in software testing that we have to test more than what is sometimes termed "the happy paths". Often we should spend at least as much effort also testing that the program handles exceptional or erroneous cases correctly.
