Perhaps you should try some spelling variations:
"su khac trac nghiem duoc hoc" » "su khac trac nghiem thuoc hoc", "su khac trac nghe duoc hoc", "su khac trai nghiem duoc hoc", "su khach trai nghiem duoc hoc", "su khai thac nghiem duoc hoc", "su khac trac nghiem quoc hoi", "vu khac trac nghiem duoc hoc", "se khac trac nghiem duoc hoc", "bui khac trac nghiem duoc hoc"
"su sach trinh nghe dai hoc" » "su sach tranh nghe dai hoc", "su hanh trinh nghe dai hoc", "su sach kinh nghe dai hoc", "su sach trinh nghien dai hoc", "su sach trinh he dai hoc", "su sach trinh nha dai hoc", "su sach trinh nghe dan hoc", "su sach trinh nghe di hoc", "su sach trinh nghe hai hoc", "so sach trinh nghe dai hoc", "vu sach trinh nghe dai hoc"

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: (("su khac trac nghiem duoc hoc") or ("su sach trinh nghe dai hoc"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("su khac trac nghiem duoc hoc") OR ("su sach trinh nghe dai hoc")).
• Removing quotes may allow a broader search: (( su khac trac nghiem duoc hoc ) or ( su sach trinh nghe dai hoc )).
• Adding a wildcard symbol may retrieve word variants: (("su khac trac nghiem duoc hoc") or ("su sach trinh nghe dai hoc"))*.