Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
hanh di » hanh vi, hanh de, hang di
y nang » ky nang, ly nang, v nang
xac va » tac va, ac va, bac va
tuc va » thuc va, truc va, tuc xa
di cua » dai cua, doi cua, de cua
x hoi » xa hoi, o hoi, x ho

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 y nang x hoi. ((hieu van) OR (hieu va)) cam ((xac va) or (tuc va)) hanh di cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang x hoi. ((hieu van) OR (hieu va)) cam ((xac va) OR (tuc va)) hanh di cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang x hoi. ((hieu van) OR (hieu va)) cam ((xac va) or (tuc va)) hanh di cua vat".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang x hoi. ((hieu van) OR (hieu va)) cam ((xac va) or (tuc va)) hanh di cua vat*.