Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh ve » hanh vi, hanh va, hanh kem
luu van » cuu van, luan van, luu hanh
luc van » luoc van, duc van, luc va
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
nang ma » tang ma, sang ma, mang may
ve cua » le cua, de cua, te cua
ve cau » ke cau, va cau, ve cac

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

• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y ((nang ma) OR (nang cao)) hoi. hieu ve cau ((luc van) OR (luu van)) hanh ve cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach y ((nang ma) or (nang cao)) hoi. hieu ve cau ((luc van) OR (luu van)) hanh ve cua tre~".
• Adding a wildcard symbol may retrieve word variants: toc sach y ((nang ma) or (nang cao)) hoi. hieu ve cau ((luc van) OR (luu van)) hanh ve cua tre*.