Perhaps you should try some spelling variations:
va thanh » gia thanh, ban thanh, va tinh
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
hieu ve » hieu va, hieu van
cac duc » cac du, cao duc, cac dac
vai cua » dai cua, hai cua, lai cua
vi cua » di cua

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 nang ma hoa. ((hieu ve) or (hieu qua)) cac duc va thanh ((vi cua) OR (vai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ma hoa. ((hieu ve) OR (hieu qua)) cac duc va thanh ((vi cua) OR (vai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ma hoa. ((hieu ve) or (hieu qua)) cac duc va thanh ((vi cua) OR (vai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ma hoa. ((hieu ve) or (hieu qua)) cac duc va thanh ((vi cua) OR (vai cua)) tre*.