$ORIGIN example.com. ; not necessary, using this to self-document $TTL 3600 @ IN SOA ns1.example.com. admin.example.com. ( 1970010100 7200 1800 1209600 300) @ ...
Apart from the source code, there seems to be virtually no public information on the web of how BIND and djbdns, amongst other recursive resolvers, select which NS servers they will query as part of ...