Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach thu » sach thue, sach thieu, sach tham
thu hanh » thuc hanh, thu thanh, thuy hanh
hanh hai » thanh hai, nhanh hai, hang hai
cua viet » ca viet, hoa viet, cua vat
hieu va » lieu va, hieu qua
cac tuc » cac toc, cac tu, cac tac
va hanh » van hanh, va thanh, ban hanh
hai cua » thai cua, dai cua, hoi cua
ca hoi » cau hoi, cua hoi, co hoi
nuoc » quoc, duoc, ngoc

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 hanh ((ca hoi) or (xa hoi)). hieu va ((cac tuc) or (hoc nuoc)) va hanh hai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach thu hanh ((ca hoi) OR (xa hoi)). hieu va ((cac tuc) OR (hoc nuoc)) va hanh hai cua viet.
• Adding a wildcard symbol may retrieve word variants: toc sach thu hanh ((ca hoi) or (xa hoi)). hieu va ((cac tuc) or (hoc nuoc)) va hanh hai cua viet*.