Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
toc sach » hoc sach, doc sach, thuoc sach
hanh ve » hanh va, hanh kem
cac ban » cac dan, cac van, can ban
cam cac » ca cac, nam cac, cam chan
van cam » van nam, van lam, van cau
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang
luu tre » luu tru, cuu tre, luy tre

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((thu sach) or (toc sach)) ky tang xa hoi. hieu van cam cac ban ((hanh ve) OR (hanh vi)) luu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (toc sach)) ky tang xa hoi. hieu van cam cac ban ((hanh ve) OR (hanh vi)) luu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) or (toc sach)) ky tang xa hoi. hieu van cam cac ban ((hanh ve) OR (hanh vi)) luu tre".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) or (toc sach)) ky tang xa hoi. hieu van cam cac ban ((hanh ve) OR (hanh vi)) luu tre*.