Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
bach tu » bach thu, cach tu, bac tu
can dan » canh dan, cac dan, can ban
vai cua » dai cua, hai cua, lai cua
tu can » tu ban, tu cac, thu canh
vi cua » di 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 ky nang ((x ho) or (xa hoi)). hieu vien bach tu can dan ((vi cua) OR (vai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((x ho) OR (xa hoi)). hieu vien bach tu can dan ((vi cua) OR (vai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((x ho) or (xa hoi)). hieu vien bach tu can dan ((vi cua) OR (vai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((x ho) or (xa hoi)). hieu vien bach tu can dan ((vi cua) OR (vai cua)) tre*.