Perhaps you should try some spelling variations:
van thiet » va thiet, dan thiet, can thiet
hieu van » hieu va, thien van, lieu va
hanh hai » thanh hai, nhanh hai, hang hai
thuc ban » thuoc ban, thuc dan, thu ban
truc ban » truc dan, truc van, truoc bang
van cac » van hac, van cau, van bac
ky danh » ky anh
ky dang » ky nang
hai van » thai van, ha van, hai tan
tu sach » thu sach, su sach, te sach

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ((ky dang) or (ky danh)) xa hoi. hieu van cac ((truc ban) or (thuc ban)) hanh hai van thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky dang) OR (ky danh)) xa hoi. hieu van cac ((truc ban) OR (thuc ban)) hanh hai van thiet.
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky dang) or (ky danh)) xa hoi. hieu van cac ((truc ban) or (thuc ban)) hanh hai van thiet*.