Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
tang van » hoang van, trong van, tang luan
hanh hoi » hanh thoi, hanh noi, hanh hoa
dang van » hoang van, hang va
ban hanh » ban hang
chat luc » chat xuc, chat lua, nhan luc
hoi cua » hoi chuc
luc ban » duc ban, cuc ban, luc bat
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
sach ty » sach y, sach tu, sach thu
hieu ve » hieu van

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 ty ((tang van) or (dang van)) hoi. ((hieu ve) OR (hieu va)) chat luc ban hanh hoi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty ((tang van) OR (dang van)) hoi. ((hieu ve) OR (hieu va)) chat luc ban hanh hoi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ty ((tang van) or (dang van)) hoi. ((hieu ve) OR (hieu va)) chat luc ban hanh hoi cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ty ((tang van) or (dang van)) hoi. ((hieu ve) OR (hieu va)) chat luc ban hanh hoi cua tre*.