Ferdinand has been removed from the UNSOURCED category although data fields have not been changed (outside the scope of the 2017 Source-a-Thon; should be reviewed by the Profile Mgs)
This source gives a different birth date (1256) than WikiTree and states that Fernando died in 1275 in Las Huelgas de Burgos, not in Allariz. It offers quite a bit of information regarding his wife, children, etc. 
Ancestry Family Trees] Family Tree files submitted by Ancestry members.
Ancestral File Number 8XJG-9B The Church of Jesus Christ of Latter-day SAINTS Publication: June 1998 (c), data as of 5 JAN 1998
Pedigree Resource File CD 49 Publication: (Salt Lake City, UT: Intellectual Reserve, Inc., 2002)
User ID: E4783FB28492436EB23CAA9C077D3F616C64
User ID: 1B2C99A9A5CF3741AF314107B55F7C86B32E
User ID: 4B2A4580C0A45142B0165FA3A67CB19C6881
Record ID Number
Record ID Number: MH:I1370
WikiTree profile De la Cerda, Infante de Castilla-1 created through the import of 20110708.ged on Jul 8, 2011 by Carlos Molina. This person was created through the import of Acrossthepond.ged on 21 February 2011. This person was created through the import of Bwiki.ged on 03 April 2011. WikiTree profile Castile-137 created through the import of jefflorrie(1).ged on Sep 10, 2011 by Jeff Johnson. This person was created through the import of Luis Manzano Dec 2010.ged on 24 April 2011. WikiTree profile De La CERDA-4 created through the import of FAMILY 6162011.GED on Jun 20, 2011 by Michael Stephenson.