Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
tham cuu » cham cuu, tham cung, thai cua
su sach » so sach
hanh ki » hanh vi, hanh ky, hanh kien
va tham » van tham, va cham, va thanh
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
vu sach » vu bach, vu khach
nang xa » nang x, nang ma, mang xa
su viet » so viet
ki su » ky su

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) OR (vu sach)) v ((nang xa) or (lang xa)) hoi. hieu va tham cuu van hanh ki su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (vu sach)) v ((nang xa) OR (lang xa)) hoi. hieu va tham cuu van hanh ki su viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) OR (vu sach)) v ((nang xa) or (lang xa)) hoi. hieu va tham cuu van hanh ki su viet".
• Adding a wildcard symbol may retrieve word variants: ((su sach) OR (vu sach)) v ((nang xa) or (lang xa)) hoi. hieu va tham cuu van hanh ki su viet*.