# Recommendation E.166 (11/1988): Numbering plan interworking in the ISDN era

> superseded recommendation/international standard from the International Telecommunication Union

**Wikidata**: [Q27051334](https://www.wikidata.org/wiki/Q27051334)  
**Source**: https://4ort.xyz/entity/recommendation-e-166-11-1988-numbering-plan-interworking-in-the-isdn-era