Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
cua viet » ca viet, hoa viet, cua vat
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
duc van » duc va, duc tan, duc manh
lam duc » lam duoc, pham duc, nam duoc
van lam » van nam
ky dang » ky nang, ky danh
ky tang » ky nang, kho tang, ky trong
cuu tre » cua tre, cau tren, cau treo

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 tang) OR (ky dang)) xa hoi. hieu van lam duc van hanh vi ((cua viet) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky tang) OR (ky dang)) xa hoi. hieu van lam duc van hanh vi ((cua viet) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky tang) OR (ky dang)) xa hoi. hieu van lam duc van hanh vi ((cua viet) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky tang) OR (ky dang)) xa hoi. hieu van lam duc van hanh vi ((cua viet) or (cuu tre))*.