Perhaps you should try some spelling variations:
"apuntes generales" » "aspectos generales", "asientos generales", "manuales generales"
"planes generales" » "plants general", "almacenes generales", "plantas general"
"temas centrales" » "las centrales", "temas penales"
"games general" » "examen general", "themes general", "viajes general"

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (((("temas centrales") or ((("planes generales") OR ("apuntes generales"))))) or ("games general"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("temas centrales") OR ((("planes generales") OR ("apuntes generales"))))) OR ("games general")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"temas centrales\") or (((\"planes generales\") OR (\"apuntes generales\"))))) or (\"games general\"))".
• Removing quotes may allow a broader search: (((( temas centrales ) or ((( planes generales ) OR ( apuntes generales ))))) or ( games general )).
• Adding a wildcard symbol may retrieve word variants: (((("temas centrales") or ((("planes generales") OR ("apuntes generales"))))) or ("games general"))*.