Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
hieu ve » hieu van
ky tang » ky nang, ky dang, kho tang
cuu tre » cua tre, cau tren, cau treo
ma hoi » mai hoi, ma hoa, me hoi
tro va » tao va, tho va, tro ba
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va
vi cuu » vi luu, vinh cuu

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