Perhaps you should try some spelling variations:
sach thu » sach thue, sach thieu, sach tham
thu nang » thi nang, thu hang, thu bang
cua viet » ca viet, hoa viet, cua dieu
te sach » toc sach
dai hoi » dai hoc, dai moi
dai hai » dai han, dai tai, dai thao
hieu va » lieu va, hieu qua
va giao » van giao, va giai, va gia
va danh » va dinh, va dan, va hanh
danh va » doanh va, hanh va, anh va

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach thu nang ((dai hoi) OR (dai hai)). hieu va giao duc va danh va ((cua viet) or (cua vat))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach thu nang ((dai hoi) OR (dai hai)). hieu va giao duc va danh va ((cua viet) OR (cua vat)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach thu nang ((dai hoi) OR (dai hai)). hieu va giao duc va danh va ((cua viet) or (cua vat))".
• Adding a wildcard symbol may retrieve word variants: te sach thu nang ((dai hoi) OR (dai hai)). hieu va giao duc va danh va ((cua viet) or (cua vat))*.