Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
van thanh » van tuan
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
tang ma » mang may, tang van
nang ma » sang ma, nang cao, mang may
cam so » nam so, ham so, cam lo
vi cua » vai cua, di cua
ve cam » ve cham, ve cac, va cam

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 ((nang ma) or (tang ma)) hoi. hieu ve cam so ((van thanh) OR (ban thanh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang ma) OR (tang ma)) hoi. hieu ve cam so ((van thanh) OR (ban thanh)) vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang ma) or (tang ma)) hoi. hieu ve cam so ((van thanh) OR (ban thanh)) vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang ma) or (tang ma)) hoi. hieu ve cam so ((van thanh) OR (ban thanh)) vi cua tre*.