Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
hieu van » hieu va, thien van, lieu va
hanh doi » thanh doi, hanh noi, hang doi
ban hanh » ban hang
chat luc » chat xuc, chat lua, nhan luc
doi cua » dai cua, hoi cua
luc ban » duc ban, cuc ban, luc bat
cua tre » cua te, cuu tre, cua triet
sach tu » sach thu, cach tu, sach ty
hieu ve » hieu va
tu tang » tuc tang, tu trang, tu tong
ma hoi » mai hoi, ma hoa, me hoi

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

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