Perhaps you should try some spelling variations:
dua tren » dung tren
cuu tre » cua tre, cau tren, cau treo
va hanh » van hanh, va thanh, va danh
cam luc » cam xuc, cau luc
hieu va » lieu va, hieu qua
tu sach » thu sach, su sach, te sach
ty hang » ly hang, ty xang, thi hang
ty tang » tay tang, ty xang, ky tang
luc va » duc va, tuc va, loc va
va cam » va cham, va cac, va cao

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 ((ty tang) OR (ty hang)) xa hoi. hieu va cam luc va hanh vi ((cuu tre) or (dua tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ty tang) OR (ty hang)) xa hoi. hieu va cam luc va hanh vi ((cuu tre) OR (dua tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ty tang) OR (ty hang)) xa hoi. hieu va cam luc va hanh vi ((cuu tre) or (dua tren))".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ty tang) OR (ty hang)) xa hoi. hieu va cam luc va hanh vi ((cuu tre) or (dua tren))*.