ITU-T Recommendation E.124 Telephone network and ISDN. Operation, numbering, routing and mobile service. Discouragement of frivolous international calling to unassigned or vacant numbers answered by recorded announcements without charge

ITU-T Recommendation E.123 Series E: Overall network operation, telephone service, service operation and human factors… General provisions concerning users. Notation for national and international telephone numbers, e-mail addresses and Web addresses ITU-T Recommendation E.122 Telephone network and ISDN. Operation, numbering, routing and mobile service. Measures to reduce customer difficulties in the international telephone service Рекомендация МСЭ-Т Е.121 Серия Е: Общая эксплуатация сети, телефонная служба, функционирование служб и человеческие факторы. Международная эксплуатация – Общие положения, касающиеся пользователей. Пиктограммы, символы и графические знаки в помощь ... ITU-T Recommendation E.125 Specifications for measuring equipment. Equipment for the measurement of digital and analogue/digital parameters. Inquiries among users of the international telephone service ITU-T Recommendation E.126 Telephone network and ISDN. Operation, numbering, routing and mobile service. Harmonization of the general information pages of the telephone directories published by administrations ITU-T Recommendation E.127 Telephone network and ISDN. Operation, numbering, routing and mobile service. Pages in the telephone directory intended for foreign visitors