Unable to find any PTR-records for the specified domain/ip :(
Log
+000
Resolving PTR record of '31.223.192.0'
+237
ERRNo PTR record availible DNS server 'pri.authdns.ripe.net' raised an NotExistentDomain error, while beeing queried for PTR-records on domain '0.192.223.31.in-addr.arpa'.