Perhaps you should try some spelling variations:
tang mai » tang ma, tang tai, lang mai
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu van
hieu va » lieu va, hieu qua
mai hoi » mai khoi, dai hoi, lai hoi
ky tang » ky nang, ky dang, kho tang
cuu tre » cua tre, cau tren, cau treo
tro va » tao va, tho va, tro ba
dao vi » dao voi, dao va, dao li
dao ve » bao ve, dap ve, dau ve

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 tang mai hoi. ((hieu ve) or (hieu va)) cac tro va ((dao vi) OR (dao ve)) cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky tang mai hoi. ((hieu ve) OR (hieu va)) cac tro va ((dao vi) OR (dao ve)) cuu tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky tang mai hoi. ((hieu ve) or (hieu va)) cac tro va ((dao vi) OR (dao ve)) cuu tre*".