Perhaps you should try some spelling variations:
"de factor" » "de facto", "dose factor", "mode factor", "de factors", "done factor", "dage factor", "de factoor", "de faitor", "e factor"
"de facts" » "de facto", "de faits", "cbe facts", "de factos", "e facts"
"e factor" » "e factors", "one factor", "age factor"
"de fact" » "de facto", "de fait", "e fact"

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"de fact\") OR (\"de facts\"))) OR (((\"de factor\") OR (\"e factor\"))))".
• Removing quotes may allow a broader search: (((( de fact ) OR ( de facts ))) OR ((( de factor ) OR ( e factor )))).
• Adding a wildcard symbol may retrieve word variants: (((("de fact") OR ("de facts"))) OR ((("de factor") OR ("e factor"))))*.