Perhaps you should try some spelling variations:
"su sach thu nghiem quoc hoi" » "su sach thu nghiem duoc hoi", "su sach thu nghiem nuoc hoi", "su sach thu nghiep quoc hoi", "su sach thuc nghiem quoc hoi", "su sach thi nghiem quoc hoi", "su sach thue nghiem quoc hoi", "su sach thieu nghiem quoc hoi", "su sach tham nghiem quoc hoi", "so sach thu nghiem quoc hoi", "vu sach thu nghiem quoc hoi"
"tu cach va nghe duc hoc" » "tu cach va nghe duoc hoc", "tu cach va nghe thuc hoc", "tu cach va nghe dung hoc", "tu cac va nghe duc hoc", "tu cach van nghe duc hoc", "tu sach va nghe duc hoc", "tu cach ta nghe duc hoc", "tu cach ve nghe duc hoc", "tu cach va nghi duc hoc", "tu cach va nghe luc hoc", "tu cach va nghe du 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 sach thu nghiem quoc hoi") or ("tu cach va nghe duc hoc"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("su sach thu nghiem quoc hoi") OR ("tu cach va nghe duc hoc")).
• Removing quotes may allow a broader search: (( su sach thu nghiem quoc hoi ) or ( tu cach va nghe duc hoc )).
• Adding a wildcard symbol may retrieve word variants: (("su sach thu nghiem quoc hoi") or ("tu cach va nghe duc hoc"))*.