Perhaps you should try some spelling variations:
thanh dai » thanh hai, thanh tai, thanh dat
hieu van » hieu va, thien van, lieu va
duc van » duc va, duc tan, duc manh
duc ban » duc tan, dua ban, duc man
cua tre » cua te, cuu tre, cua triet
tang ma » mang may, tang van
hieu ve » hieu va
ky tang » ky nang, ky dang, kho tang
sac ky » cac ky, sai ky
ma hoi » mai hoi, xa hoi, ma hoa
su sac » su sach, su cac, su xac

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sac ky tang ma hoi. ((hieu ve) OR (hieu van)) cam ((duc ban) or (duc van)) thanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sac ky tang ma hoi. ((hieu ve) OR (hieu van)) cam ((duc ban) OR (duc van)) thanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sac ky tang ma hoi. ((hieu ve) OR (hieu van)) cam ((duc ban) or (duc van)) thanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: su sac ky tang ma hoi. ((hieu ve) OR (hieu van)) cam ((duc ban) or (duc van)) thanh dai cua tre*.