Perhaps you should try some spelling variations:
"lettres patents" » "letters patents", "letters patent", "lettres pates", "letters patentss"
"lettres patentes" » "letters patentes", "lettres patees", "letters patentses"
"lettres patent" » "letters patent", "lettres pate", "letters patents"

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: (("lettres patentes") OR ((("lettres patent") OR ("lettres patents")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"lettres patentes\") or (((\"lettres patent\") OR (\"lettres patents\"))))".
• Removing quotes may allow a broader search: (( lettres patentes ) or ((( lettres patent ) OR ( lettres patents )))).
• Adding a wildcard symbol may retrieve word variants: (("lettres patentes") or ((("lettres patent") OR ("lettres patents"))))*.