What is the most recent Casper FFG specification?

Hi, I’m looking for the most recent Casper FFB spec for Eth2.0.

On Eth2.0 github pages there is noting about Casper.

The arxiv paper: Casper the Friendly Finality Gadget got some updates, but didn’t have time to analyze changes, so not sure if it’s just minor / style updates or the updates to the most recent spec.

Also, is @vbuterin Casper Note still up-to-date?

All best.