# Other databases

Here is a list of some other Metamath databases that we know of but are not
included in this repository (sorted alphabetically by GitHub ID):

* @david-a-wheeler's collection of [test databases](https://github.com/david-a-wheeler/metamath-test).
* @digama0's [Dependent-Type Theory](https://github.com/digama0/dtt.mm/blob/master/dtt.mm).
* @geohot's [TwitchCoq](https://github.com/geohot/twitchcoq/blob/master/metamath/realtwoplustwo.mm) has a few interesting 2+2 proofs.
* @ishanpm's [Linear Logic](https://github.com/ishanpm/metamathlinear/blob/master/linear.mm).
* @jamesjer's [Unlimited Register Machine and Hilbert Geometry](https://github.com/jamesjer/set.mm/blob/geometry/set.mm) is a fork of set.mm with very interesting work which has not been merged back.
* @naipmoro's [Laws of Form](https://naipmoro.github.io/lofmm/).
* @pbrosnan's [Number Theory Game](https://github.com/pbrosnan/ntg) based on peano.mm, with additions.
* @rod-lin's [Matching Logic](https://github.com/rod-lin/kore2mm/blob/master/prelude.mm) - the result of a Kore-to-MM conversion.
* @sctfn's older version of [New Foundations](https://github.com/sctfn/metamath-nf/blob/master/nf.mm) (this has since been moved into this repository).
* @sorear's [A variation on Peano](https://github.com/sorear/metamath-stuff/blob/master/yapeano.mm), whose goal is to treat Peano arithmetic as a first-order theory with terms.
* @tirix's [FOL without overloading](https://github.com/tirix/set-noov.mm).
* @tirix's [Q0 Logic](https://github.com/tirix/q0.mm).

*Anyone* can create a Metamath database, but we thought linking to some of them
might be of use.
