Perhaps you should try some spelling variations:
vat thanh » dat thanh, gat thanh, tat thanh
thu sach » tu sach, thuat sach, thuoc sach
hieu van » thien van, lieu va, hieu ve
nam thuc » nam thuoc, am thuc, nam thu
hieu va » lieu va, hieu qua
y nang » ky nang, ly nang, v nang
do van » dao van, vo van, so van
x hoi » xa hoi, o hoi, x ho
do va » so va

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach y nang x hoi. ((hieu van) or (hieu va)) nam thuc vat thanh ((do va) OR (do van)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach y nang x hoi. ((hieu van) OR (hieu va)) nam thuc vat thanh ((do va) OR (do van)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach y nang x hoi. ((hieu van) or (hieu va)) nam thuc vat thanh ((do va) OR (do van)) triet".
• Adding a wildcard symbol may retrieve word variants: thu sach y nang x hoi. ((hieu van) or (hieu va)) nam thuc vat thanh ((do va) OR (do van)) triet*.