# Twelvefold way

> systematic classification of 12 related enumerative problems concerning two finite sets

**Wikidata**: [Q7857666](https://www.wikidata.org/wiki/Q7857666)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Twelvefold_way)  
**Source**: https://4ort.xyz/entity/twelvefold-way