When i do this:

Code:
nslookup -type=ns zlatapraha.cz
;; Got SERVFAIL reply from 8.8.8.8, trying next server
;; Got SERVFAIL reply from 8.8.8.8, trying next server
Server:         8.8.4.4
Address:        8.8.4.4#53

** server can't find zlatapraha.cz: SERVFAIL
I get an error, but in whois output of this domain im getting nameservers. Why it failed?

Here is another domain .cz which dont fails...

Code:
nslookup -type=ns seznam.cz
Server:         8.8.8.8
Address:        8.8.8.8#53

Non-authoritative answer:
seznam.cz       nameserver = ms.seznam.cz.
seznam.cz       nameserver = ns.seznam.cz.

Authoritative answers can be found from:
Im interested how to fix the failure with first domain, why it dont output nameservers?

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another serv fail im getting with domain: vpscorner.co.uk for example