# Tweet by [@keefmoon](http://twitter.com/keefmoon) on 2019-07-24 16:05:58 > [!INFO] Archived from [original tweet](http://twitter.com/keefmoon/status/1154060161524412418) I seen them used, but never saw them this clearly defined, and I no idea as to the provenance. https://t.co/aiTsPMlXrt