Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach ky » sac ky, sach y, sach ty
hanh ve » hanh vi, hanh va
luc van » luoc van, luu van, duc van
cau luc » cau truc, cau phuc
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
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 ((nang xa) OR (nang ma)) hoi. hieu ve cau luc van ((hanh ve) or (hanh kem)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky ((nang xa) OR (nang ma)) hoi. hieu ve cau luc van ((hanh ve) OR (hanh kem)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky ((nang xa) OR (nang ma)) hoi. hieu ve cau luc van ((hanh ve) or (hanh kem)) cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ky ((nang xa) OR (nang ma)) hoi. hieu ve cau luc van ((hanh ve) or (hanh kem)) cua tre*.