Perhaps you should try some spelling variations:
trinh nghien » kinh nghiem, trinh thiet, trinh dien
trai nghiem » trac nghiem, thi nghiem
trinh nghe » trinh he, trinh nha
khach trai » khac trai, khanh tra, kham trai
nghiem du » nghiem dau, nghiem d, nghiem de
su khach » vu khach, su khac, cua khach
vu sach » vu bach, su sach, vu khach
su hoc » tu hoc, so hoc, su ho
du hoc » tu hoc, duoc hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( vu sach ((trinh nghe) OR (trinh nghien)) su hoc ) or ( su khach trai nghiem du hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( vu sach ((trinh nghe) OR (trinh nghien)) su hoc ) OR ( su khach trai nghiem du hoc ))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( vu sach ((trinh nghe) OR (trinh nghien)) su hoc ) or ( su khach trai nghiem du hoc ))*".