800 Service Management System - http://www.sms800.com/
Information about the central database for US toll free number management. |
Area Code Information - http://www.areacode-info.com/
Detailed information on the history and current developments in North American NPA allocations. |
International Numbering Plans - http://www.numberingplans.com/
A collection of all international numbering plans in the world. Some features require a paid subscription. |
The Telephone Exchange Name Project - http://ourwebhome.com/TENP/TENproject.html
The historical relationship between North American telephone exchange names and numbers. |