Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
ty dang » ty xang, ky dang, ty hang
dang ma » dang mau, dang mam, dang mat
hieu ve » hieu van
hieu va » lieu va, hieu qua
tro cap » trong cap, trot cay, theo cap
cap dan » cac dan, ca dan, cay dan
cua tre » cua te, cuu tre, cua triet
dan vi » doan vi, don vi, dan va
vi cua » vai cua, di cua

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 ty dang ma hoa. ((hieu ve) or (hieu va)) cac tro cap dan vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty dang ma hoa. ((hieu ve) OR (hieu va)) cac tro cap dan vi cua tre*.