Perhaps you should try some spelling variations:
da nang » cam nang, kha nang, cao nang
xa dong » ha dong, van dong, lao dong
cac toc » cac toi, cac nuoc, cac thoi
sach ky » sac ky, sach y, sach ty
su sach » so sach, vu sach
van hoc » van hoa
van hoi » van hoa, van hoe, van loi
ky lang » ky nang, ky dang, ky tang
hieu ve » hieu va, hieu van
ve cac » va cac, vien cac
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: su sach ky lang ((van hoi) OR (van hoc)). hieu ve cac toc ((xa dong) or (da nang)) hoi va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky lang ((van hoi) OR (van hoc)). hieu ve cac toc ((xa dong) OR (da nang)) hoi va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky lang ((van hoi) OR (van hoc)). hieu ve cac toc ((xa dong) or (da nang)) hoi va thiet".
• Adding a wildcard symbol may retrieve word variants: su sach ky lang ((van hoi) OR (van hoc)). hieu ve cac toc ((xa dong) or (da nang)) hoi va thiet*.