Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
ky tang » ky nang, ky dang, kho tang
tang xa » trang xa, tang ma, lang xa
hieu va » lieu va, hieu qua
cau tre » cau treo, cau tra, cuu tre
hanh ve » hanh vi, hanh va, hanh kem
tu san » thu san, tu ban, tu can
san ky » sang ky, van ky, dan ky
va cau » van cau, va cac, va dau
luc va » tuc va, loc va

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu san ky tang xa hoi. hieu va cau ((luc va) or (duc va)) hanh ve ((cau tre) OR (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu san ky tang xa hoi. hieu va cau ((luc va) OR (duc va)) hanh ve ((cau tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu san ky tang xa hoi. hieu va cau ((luc va) or (duc va)) hanh ve ((cau tre) OR (cau tren))".
• Adding a wildcard symbol may retrieve word variants: tu san ky tang xa hoi. hieu va cau ((luc va) or (duc va)) hanh ve ((cau tre) OR (cau tren))*.