Perhaps you should try some spelling variations:
van thiet » va thiet, dan thiet, can thiet
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
ve cham » va cham, vu cham, ve chim
ve chat » va chat, van chat
va hanh » va thanh, va danh, ban hanh
ma hoi » mai hoi, xa hoi, ma hoa

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 nang ma hoi. hieu ((ve cham) OR (ve chat)) xuc ((va hanh) or (van hanh)) vi van thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ma hoi. hieu ((ve cham) OR (ve chat)) xuc ((va hanh) OR (van hanh)) vi van thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ma hoi. hieu ((ve cham) OR (ve chat)) xuc ((va hanh) or (van hanh)) vi van thiet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ma hoi. hieu ((ve cham) OR (ve chat)) xuc ((va hanh) or (van hanh)) vi van thiet*.