Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, hieu ve
tu sach » thu sach, su sach, te sach
truc va » thuc va, thuc vat, trung va
y nang » ky nang, ly nang, v nang
va dan » ca dan, va dao, va dau
di cua » dai cua, doi cua, do cua
de cua » le cua, te cua, dieu 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 (lieu va)) cau truc va dan ((di cua) or (de cua)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang x hoi. ((hieu van) OR (lieu va)) cau truc va dan ((di cua) OR (de cua)) viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang x hoi. ((hieu van) OR (lieu va)) cau truc va dan ((di cua) or (de cua)) viet".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang x hoi. ((hieu van) OR (lieu va)) cau truc va dan ((di cua) or (de cua)) viet*.