server1.gts.cz has no CNAME records.
Question and response
Question
dig server1.gts.cz. NS
Answer
The response has no answer records.
Authority
gts.cz. 71731 SOA ns.inecnet.cz. hostmaster.cz.net. 2025110402 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0