Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, hieu ve
cac truc » cau truc, cac tru, cac trung
su sach » so sach, vu sach
nang xa » nang x, lang xa, nang ma
truc va » thuc va, thuc vat, trung va
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo
y nang » ky nang, ly nang, v nang
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su sach y nang xa hoi. ((hieu van) OR (lieu va)) cac truc va dan vi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y nang xa hoi. ((hieu van) OR (lieu va)) cac truc va dan vi ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y nang xa hoi. ((hieu van) OR (lieu va)) cac truc va dan vi ((cua tre) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: su sach y nang xa hoi. ((hieu van) OR (lieu va)) cac truc va dan vi ((cua tre) or (cuu tre))*.