Perhaps you should try some spelling variations:
cam truc » cau truc, nam truc, lam truoc
duy sang » duy van, duy can, duy anh
tu sach » thu sach, su sach, te sach
mai hoi » mai khoi, dai hoi, lai hoi
hieu ve » hieu van
va hanh » van hanh, va thanh, va danh
hieu va » lieu va, hieu qua
truc va » thuc va, thuc vat, trung va
vi cua » vai cua, di cua
cua te » cua tu

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