These entries are queried from radb.net using whois, you can try my project getting these.
:AS-TUMBLR as-set: AS-TUMBLR descr: Tumblr, Inc. remarks: New York, NY remarks: http://as33612.net/ members: AS33612 admin-c: MPE54-ARIN tech-c: MPE54-ARIN notify: peterson [at] tumblr.com mnt-by: MAINT-AS33612 changed: peterson [at] tumblr.com 20111117 source: ALTDB