Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
vien cac » vien bach, vien dai, vien da
dai hoi » dai hoc, dai hai, dai moi
lai hoi » lai hoa, lai roi, mai hoi
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
va danh » va dinh, va dan, va hanh
tu sach » thu sach, su sach, te sach
vi cua » vai cua
di cua » dai cua, doi cua, de cua

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 ty nang ((lai hoi) or (dai hoi)). hieu vien cac nuoc va danh ((vi cua) OR (di cua)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ((lai hoi) OR (dai hoi)). hieu vien cac nuoc va danh ((vi cua) OR (di cua)) viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang ((lai hoi) or (dai hoi)). hieu vien cac nuoc va danh ((vi cua) OR (di cua)) viet".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ((lai hoi) or (dai hoi)). hieu vien cac nuoc va danh ((vi cua) OR (di cua)) viet*.