sorry.southern.usta.com has no NS records.
NS records for this zone are defined at usta.com.
NS records for this zone are defined at usta.com.
Question and response
Question
dig sorry.altdc3.va.twimm.net. NS
Answer
The response has no answer records.
Authority
twimm.net. 3601 SOA dns1.registrar-servers.com. hostmaster.registrar-servers.com. 1772992240 43200 3600 604800 3601
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0