Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
hieu van » hieu va, thien van, lieu va
cau tren » cu tren, dau tren, ca tren
lang xa » lang ha, dang xay, lang van
van hau » van ha, van hai, van dau
luc van » luoc van, luu van, duc van
nang xa » nang x, nang ma, mang xa
hanh de » hanh ve, hanh kem
cua tre » cua te, cuu tre, cua triet
hau luc » hau loc, cau luc, nhan luc

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