I must be looking at a different document. The "EWD831" link on my device takes me to https://www.cs.utexas.edu/users/EWD/ewd08xx/EWD831.PDF https://www.cs.utex

I must be looking at a different document. The "EWD831" link on my device takes me to https://www.cs.utexas.edu/users/EWD/ewd08xx/EWD831.PDF https://www.cs.utexas.edu/users/EWD/ewd08xx/EWD831.PDF which is a 2-colour scan of a typed page. Edit: I can't explain how, but the first time I downloaded that PDF I received a file which looked different. Here is a similar file from the same site which clearly resembles what led me to make the comment above: https://www.cs.utexas.edu/users/EWD/ewd00xx/EWD77.PDF https://www.cs.utexas.edu/users/EWD/ewd00xx/EWD77.PDF So I apologise for this unnecessary diversion from the topic.