Perhaps you should try some spelling variations:
"khoa luan hoa dan toc." » "khoa luan khoa dan toc." (Expand Search), "khoa xuan hoa dan toc." (Expand Search), "khoa luan hoi dan toc." (Expand Search)
"khoa luan mot dan toc." » "khoa luat mot dan toc." (Expand Search), "khoa gian mot dan toc." (Expand Search), "khoa luan co dan toc." (Expand Search), "khoa luan mot lan toc." (Expand Search), "khoa luan mot san toc." (Expand Search), "khoa luan mat dan toc." (Expand Search)
"khoa luan tot dan toc." » "khoa luan tot dinh toc." (Expand Search), "khoa luan hoat dan toc." (Expand Search), "khoa luan mot dang toc." (Expand Search)

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("khoa luan hoa dan toc.") OR ((("khoa luan tot dan toc.") OR ("khoa luan mot dan toc."))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"khoa luan hoa dan toc.\") OR (((\"khoa luan tot dan toc.\") OR (\"khoa luan mot dan toc.\"))))".
• Removing quotes may allow a broader search: (( khoa luan hoa dan toc. ) OR ((( khoa luan tot dan toc. ) OR ( khoa luan mot dan toc. )))).
• Adding a wildcard symbol may retrieve word variants: (("khoa luan hoa dan toc.") OR ((("khoa luan tot dan toc.") OR ("khoa luan mot dan toc."))))*.