Perhaps you should try some spelling variations:
sach tham » sach nha
sach thu » sach thue, sach thieu, cach thuc
van hanh » van thanh, ban hanh, van anh
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
cac duc » cac du, cao duc, cac dac
va hanh » va thanh, va danh, ban hanh
tai cua » thai cua, tai cuc, tri cua
cua tre » cua te, cuu tre, cua triet

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