Perhaps you should try some spelling variations:
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
so sach » so sanh, bo sach, co sach
sach tu » sach thu, cach tu, sach ty
tu lang » cu lang, tu lanh, xu lang
lang xa » lang ha, dang xay, lang van
hieu ve » hieu va, hieu van
cac toc » cac toi, cac thoi
da nang » cam nang, kha nang, cao nang
thiet » thieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach tu lang xa hoi. hieu ve ((cac toc) OR (cac nuoc)) ((van dong) or (da nang)) hoi va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach tu lang xa hoi. hieu ve ((cac toc) OR (cac nuoc)) ((van dong) OR (da nang)) hoi va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach tu lang xa hoi. hieu ve ((cac toc) OR (cac nuoc)) ((van dong) or (da nang)) hoi va thiet".
• Adding a wildcard symbol may retrieve word variants: so sach tu lang xa hoi. hieu ve ((cac toc) OR (cac nuoc)) ((van dong) or (da nang)) hoi va thiet*.