Perhaps you should try some spelling variations:
trinh nghien » trinh nghe, kinh nghiem, trinh dien
trinh thiet » trinh viet, trinh thi
khach trac » khach trai, khanh trach, khac trai
nghiem ban » nghiem van, nghiem xuan, nghiep bang
nha khach » he khach, cua khach
duoc hoc » quoc hoi
te sach » toc sach
ban hoc » bang hoc, van hoc, bai hoc

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

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