Perhaps you should try some spelling variations:
"model factors" » "models factors", "model factor", "model factory", "model factrs", "model factsrs"
"de factores" » "de actores", "que factores", "de sectores", "e factores", "dose factores", "mode factores", "de factres", "de factsres"
"de factor" » "e factor", "dose factor", "mode factor", "de factr", "de factsr"
"de facto" » "de fact", "de facts"

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (((("de facto") OR ("de factor"))) OR ((("de factores") OR ("model factors")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"de facto\") OR (\"de factor\"))) or (((\"de factores\") or (\"model factors\"))))".
• Removing quotes may allow a broader search: (((( de facto ) OR ( de factor ))) or ((( de factores ) or ( model factors )))).
• Adding a wildcard symbol may retrieve word variants: (((("de facto") OR ("de factor"))) or ((("de factores") or ("model factors"))))*.