Perhaps you should try some spelling variations:
dua tren » dung tren
ban hanh » ban hang
te sach » toc sach
sach ky » sac ky, sach y, sach ty
duc ban » duc tan, duc van, dua ban
cuu tre » cua tre, cau tren, cau treo
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
ve cao » va cao, ve cac, ve co
ve bao » te bao, va bao
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ky tang ma hoi. hieu ((ve cao) OR (ve bao)) duc ban hanh vi ((dua tren) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky tang ma hoi. hieu ((ve cao) OR (ve bao)) duc ban hanh vi ((dua tren) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky tang ma hoi. hieu ((ve cao) OR (ve bao)) duc ban hanh vi ((dua tren) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: te sach ky tang ma hoi. hieu ((ve cao) OR (ve bao)) duc ban hanh vi ((dua tren) or (cuu tre))*.