Perhaps you should try some spelling variations:
vien can » vien canh, vien cac, vien cao
viec can » viec ban, view can, viec cong
cua viet » ca viet, hoa viet, cua vat
lai hoa » dai hoa, loai hoc
sach ty » sach y, sach tu, sach thu
mai hoi » mai khoi, dai hoi, lai hoi
ty nang » ky nang, ty xang, ty hang
va hanh » van hanh, va thanh, va danh
tu sach » thu sach, su sach, te sach
vi cua » vai cua, di cua

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ((mai hoi) OR (lai hoa)). hieu ((viec can) OR (vien can)) nuoc va hanh vi cua viet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang ((mai hoi) or (lai hoa)). hieu ((viec can) OR (vien can)) nuoc va hanh vi cua viet~".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ((mai hoi) or (lai hoa)). hieu ((viec can) OR (vien can)) nuoc va hanh vi cua viet*.