spf4.tamu.edu has no NS records.
NS records for this zone are defined at tamu.edu.
NS records for this zone are defined at tamu.edu.
Question and response
Question
dig spf4.tamu.edu. NS
Answer
The response has no answer records.
Authority
tamu.edu. 900 SOA csce-info-grid.net.tamu.edu. infoblox.tamu.edu. 11426901 14400 1440 2419200 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0