glue record

I'm looking for glue record for so I ask one of the root
name server.
It gives me the list of dot mobi authorized name servers.

I'm expecting it to be answered by one of the mobi tld authorized name
servers, but it's telling me that it delegates the answer to instead. It does not make sense for me because how can I
ask if I don't know its ip address yet...
Clue please..?

  Did you bother to read the response? The glue records are
  in the *additional* section. Iterative resolvers know to
  look in the additional section to find glue records.