Perhaps you should try some spelling variations:
"khoa hoc thong thuc." » "khoa hoc thuong thuc." (Expand Search), "khoa hoc thong thu." (Expand Search), "khoa hoc chong thuc." (Expand Search), "khoa hoa thong thuc." (Expand Search), "khoa hoc phuong thuc." (Expand Search), "khoa he thong thuc." (Expand Search), "hoa hoc thong thuc." (Expand Search)
"khoa hoc trong thuc." » "khoa hoc trong thu." (Expand Search), "khoa hoc thuong thuc." (Expand Search), "khoa hoc trong tho." (Expand Search), "khoa hoc trung thuc." (Expand Search), "khoa hoc cong thuc." (Expand Search), "hoa hoc trong thuc." (Expand Search)
"khoa hoc trong thoi." » "khoa hoc trong boi." (Expand Search), "khoa hoc trung thoi." (Expand Search), "khoa hoc cong thoi." (Expand Search), "hoa hoc trong thoi." (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 thong thuc.") OR ((("khoa hoc trong thuc.") OR ("khoa hoc trong thoi."))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"khoa hoc thong thuc.\") OR (((\"khoa hoc trong thuc.\") OR (\"khoa hoc trong thoi.\"))))".
• Removing quotes may allow a broader search: (( khoa hoc thong thuc. ) OR ((( khoa hoc trong thuc. ) OR ( khoa hoc trong thoi. )))).
• Adding a wildcard symbol may retrieve word variants: (("khoa hoc thong thuc.") OR ((("khoa hoc trong thuc.") OR ("khoa hoc trong thoi."))))*.