# abacus

> calculating tool

**Wikidata**: [Q12806](https://www.wikidata.org/wiki/Q12806)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Abacus)  
**Source**: https://4ort.xyz/entity/abacus


## References

1. Freebase Data Dumps. 2013
2. Nuovo soggettario
3. National Library of Israel
4. [Bibliography of the History of the Czech Lands](https://biblio.hiu.cas.cz/records/63df099e-db44-46f1-8aad-b620e3e6927b)