Perhaps you should try some spelling variations:
duy sang » duy van, duy can, duy anh
cac truc » cau truc, cac tru, cac trung
te sach » toc sach
mai hoi » mai khoi, dai hoi, lai hoi
hieu ve » hieu va, hieu van
truc va » thuc va, thuc vat, trung va
va hanh » van hanh, va thanh, va danh
ve cac » va cac, vien cac
cua tu » cua tuc, cua su, cua cu

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

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