ptr1.twnic.net.tw has no NS records.
NS records for this zone are defined at twnic.net.tw.
NS records for this zone are defined at twnic.net.tw.
Question and response
Question
dig ptr1.twnic.net.tw. NS
Answer
The response has no answer records.
Authority
twnic.net.tw. 1800 SOA dns.nic.net.tw. snw.twnic.net.tw. 1773018001 7200 1800 2419000 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0