Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
truc van » truc va, thuc van, truc ban
hanh ve » hanh vi, hanh va
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
nang ma » tang ma, sang ma, nang cao
lang xa » lang ha, dang xay, lang van
cua tre » cua te, cuu tre, cua triet
ve cau » ke cau, va cau, ve cac

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ky ((lang xa) or (nang ma)) hoi. hieu ve cau truc van ((hanh ve) or (hanh kem)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky ((lang xa) OR (nang ma)) hoi. hieu ve cau truc van ((hanh ve) OR (hanh kem)) cua tre.
• Adding a wildcard symbol may retrieve word variants: toc sach ky ((lang xa) or (nang ma)) hoi. hieu ve cau truc van ((hanh ve) or (hanh kem)) cua tre*.