Spain's Virtual Defence Library catalogs a 28-page military dossier on the 12 November 1976 report at Talavera la Real Air Base, including its declassification status and digitized images.
This is the core institutional source for the Talavera case because it establishes the file's provenance, date, size and official custody.
The catalog proves that a military report and investigation exist. It does not independently verify the guards' figure description or identify an extraordinary origin. Original source: https://bibliotecavirtual.defensa.gob.es/BVMDefensa/exp_ovni/es/consulta/registro.do?control=BMDB20160069099