Perhaps you should try some spelling variations:
"sung and moon letters" » "dung and moon letters", "cung and moon letters", "ung and moon letters", "sung and mon letters", "sung and muon letters", "sung and soon letters"
"song and moon letters" » "song and mon letters", "song and muon letters", "song and soon letters", "cong and moon letters", "dong and moon letters"
"song and yoon letters" » "cong and yoon letters", "dong and yoon letters"

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

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