Não informado. (1989). NTT Review. Nippon Telegraph and Telephone Corporation.
Chicago-viite (17. p.)Não informado. NTT Review. Tokyo: Nippon Telegraph and Telephone Corporation, 1989.
MLA-viite (8. p.)Não informado. NTT Review. Nippon Telegraph and Telephone Corporation, 1989.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.