Perhaps you should try some spelling variations:
thai nghien » thai nguyen, thi nghiem, phan nghien
sach trac » sach truc, sach tranh, sach tham
trac nghe » trac nghiem, thai nghe, cac nghe
nghe duoc » nghiem duoc, nghe nuoi, che duoc
duoc hoc » quoc hoi
su sach » so sach, vu sach
xu hoc » tu hoc, du hoc, su hoc

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 ((thai nghien) OR (phap nghien)) xu hoc ) or ( su sach trac nghe duoc hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( su sach ((thai nghien) OR (phap nghien)) xu hoc ) OR ( su sach trac nghe duoc hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( su sach ((thai nghien) OR (phap nghien)) xu hoc ) or ( su sach trac nghe duoc hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( su sach ((thai nghien) OR (phap nghien)) xu hoc ) or ( su sach trac nghe duoc hoc ))*.