Nippon Telegraph & Telephon Public Corporation. (1981). Guide to NTT. Tokyo: Nippon Telegraph & Telephon Public Corporation.
Chicago Stili AlıntıNippon Telegraph & Telephon Public Corporation. Guide to NTT. Tokyo: Nippon Telegraph & Telephon Public Corporation, 1981.
MLA AlıntıNippon Telegraph & Telephon Public Corporation. Guide to NTT. Tokyo: Nippon Telegraph & Telephon Public Corporation, 1981.
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