Perhaps you should try some spelling variations:
thanh vai » thanh hai, thanh van, thanh tai
hoc sach » hoc sinh, hoc cac, hoc anh
hieu van » hieu va, thien van, lieu va
hieu ve » hieu va
sach ky » sac ky, sach y, sach ty
duc ban » duc tan, dua ban, duc man
duc van » duc va, duc tan, duc manh
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
ma hoi » mai hoi, xa hoi, ma hoa
vai va » mai va, dai va, hai va
thiet* » thieu*

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach ky tang ma hoi. ((hieu ve) or (hieu van)) cam ((duc ban) OR (duc van)) thanh vai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ky tang ma hoi. ((hieu ve) OR (hieu van)) cam ((duc ban) OR (duc van)) thanh vai va thiet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ky tang ma hoi. ((hieu ve) or (hieu van)) cam ((duc ban) OR (duc van)) thanh vai va thiet*".