sokol.netforce.cz has no NS records.
NS records for this zone are defined at netforce.cz.
NS records for this zone are defined at netforce.cz.
Question and response
Question
dig sokol.netforce.cz. NS
Answer
The response has no answer records.
Authority
netforce.cz. 86400 SOA server1.gts.cz. hostmaster.cz.net. 2007080919 28800 7200 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0