Perhaps you should try some spelling variations:
"khoa hoc trong thoi." » "khoa hoc trong boi." (Expand Search), "khoa hoc cong thoi." (Expand Search), "hoa hoc trong thoi." (Expand Search)
"khoa hoc trung thu." » "khoa dac trung thu." (Expand Search), "khoa hoc truong thu." (Expand Search), "khoa hoc tung thu." (Expand Search), "khoa hoc trung tu." (Expand Search), "hoa hoc trung thu." (Expand Search)
"khoa hoc trong thu." » "khoa hoc cong thu." (Expand Search), "khoa hoc dong thu." (Expand Search), "hoa hoc trong thu." (Expand Search)

Try widening your search to All Fields.

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("khoa hoc trung thu.") OR ((("khoa hoc trong thu.") OR ("khoa hoc trong thoi."))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"khoa hoc trung thu.\") OR (((\"khoa hoc trong thu.\") OR (\"khoa hoc trong thoi.\"))))".
• Removing quotes may allow a broader search: (( khoa hoc trung thu. ) OR ((( khoa hoc trong thu. ) OR ( khoa hoc trong thoi. )))).
• Adding a wildcard symbol may retrieve word variants: (("khoa hoc trung thu.") OR ((("khoa hoc trong thu.") OR ("khoa hoc trong thoi."))))*.