Perhaps you should try some spelling variations:
"dang thuyet trinh." » "dang thuyet lich." (Expand Search), "nang thuyet trinh." (Expand Search), "giang thuyet trinh." (Expand Search), "dang thuy trinh." (Expand Search)
"dang thuc tinh." » "dang thi tinh." (Expand Search), "dang thai tinh." (Expand Search), "dang thuoc tinh." (Expand Search), "dang thuy tinh." (Expand Search), "dang thu tinh." (Expand Search)
"dan thuc tinh." » "dan thuoc tinh." (Expand Search), "dan thuy tinh." (Expand Search), "dan thu tinh." (Expand Search), "nhan thuc tinh." (Expand Search), "dan toc tinh." (Expand Search), "am thuc tinh." (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: (("dang thuyet trinh.") OR ((("dang thuc tinh.") OR ("dan thuc tinh."))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"dang thuyet trinh.\") OR (((\"dang thuc tinh.\") OR (\"dan thuc tinh.\"))))".
• Removing quotes may allow a broader search: (( dang thuyet trinh. ) OR ((( dang thuc tinh. ) OR ( dan thuc tinh. )))).
• Adding a wildcard symbol may retrieve word variants: (("dang thuyet trinh.") OR ((("dang thuc tinh.") OR ("dan thuc tinh."))))*.