Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
cua tre » cuu tre, cua triet, dua tren
ve bac » ve bao, ve cac, ve ban
cua te » cua tu
x hoi » xa hoi, o hoi, x ho
bo va » bao va, do va, co va
so va » so van, so vat, su va

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 hoi. hieu ve bac ((bo va) or (so va)) hanh vi ((cua tre) OR (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x hoi. hieu ve bac ((bo va) OR (so va)) hanh vi ((cua tre) OR (cua te)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x hoi. hieu ve bac ((bo va) or (so va)) hanh vi ((cua tre) OR (cua te))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x hoi. hieu ve bac ((bo va) or (so va)) hanh vi ((cua tre) OR (cua te))*.