I’ve released a new version of my free math ebook.

The main feature of this new release is chapter “Alternative representations of binary relations” where I essentially claim that the following are the same:

- binary relations
- pointfree funcoids between powersets
- Galois connections between powersets
- antitone Galois connections between powersets

This theorem is presented with a commutative diagram.

I have added also some other minor theorems.