dns.ntt.RU has no NS records.
NS records for this zone are defined at ntt.RU.
NS records for this zone are defined at ntt.RU.
Question and response
Question
dig dns.ntt.RU. NS
Answer
The response has no answer records.
Authority
ntt.ru. 3600 SOA ns.ntt.ru. george.ntt.ru. 20091587 86400 7200 3600000 172800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0