Perhaps you should try some spelling variations:
"sung and moon letters" » "dung and moon letters", "song and moon letters", "cung and moon letters", "sung and mon letters", "sung and muon letters", "sung and soon letters"
"dong and moon letters" » "dong and mon letters", "dong and muon letters", "dong and soon letters", "cong and moon letters", "dung and moon letters"
"dong and yoon letters" » "cong and yoon letters", "dung 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 ((("dong and moon letters") OR ("dong and yoon letters"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("sung and moon letters") OR ((("dong and moon letters") OR ("dong and yoon letters")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"sung and moon letters\") or (((\"dong and moon letters\") OR (\"dong and yoon letters\"))))".
• Removing quotes may allow a broader search: (( sung and moon letters ) or ((( dong and moon letters ) OR ( dong and yoon letters )))).
• Adding a wildcard symbol may retrieve word variants: (("sung and moon letters") or ((("dong and moon letters") OR ("dong and yoon letters"))))*.