Perhaps you should try some spelling variations:
hieu vien » hieu hien, thieu nien, hieu tieng
hieu viec » nhieu viec, hieu ve, sieu viet
dua tren » dung tren
dinh vai » dinh van, dinh vi, dinh va
va triet » va thiet, va trien, ve triet
sach ky » sac ky, sach y, sach ty
bach lo » sach lo, bach hoa, bach mao
va dinh » van dinh, va kinh, va tinh
tu sach » thu sach, su sach, te sach
nang o » nang co, nang ho, nang ro
lo va » lo van, lao va, ly va
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang o hoi. ((hieu vien) OR (hieu viec)) bach lo va dinh vai ((dua tren) or (va triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang o hoi. ((hieu vien) OR (hieu viec)) bach lo va dinh vai ((dua tren) OR (va triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang o hoi. ((hieu vien) OR (hieu viec)) bach lo va dinh vai ((dua tren) or (va triet))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang o hoi. ((hieu vien) OR (hieu viec)) bach lo va dinh vai ((dua tren) or (va triet))*.