Perhaps you should try some spelling variations:
dua tren » dung tren
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
va hanh » van hanh, va thanh, va danh
cuu tre » cua tre, cau tren, cau treo
nang ma » tang ma, sang ma, nang cao
le cap » le cau
ve tai » te tai, de tai, le tai
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: tu sach ky nang ma hoi. hieu ((le cap) or (ve tai)) nuoc va hanh vi ((dua tren) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ma hoi. hieu ((le cap) OR (ve tai)) nuoc va hanh vi ((dua tren) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ma hoi. hieu ((le cap) or (ve tai)) nuoc va hanh vi ((dua tren) or (cuu tre))*.