Perhaps you should try some spelling variations:
va triet » va thiet, va trien, ve triet
thanh di » thanh doi, thanh de, thanh do
va thanh » gia thanh, ban thanh, va tinh
nam thuc » nam thuoc, nam thu, nam tu
hieu van » hieu va, thien van, lieu va
cao hoi » cau hoi, co hoi, cao hoc
sach va » sach xa, sach dao, sach nha
sach ha » sach nha, sach han, sach xa
di va » dai va, di vao, doi va

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 va) OR (sach ha)) nang cao hoi. hieu van ((am thuc) or (nam thuc)) va thanh di va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach va) OR (sach ha)) nang cao hoi. hieu van ((am thuc) OR (nam thuc)) va thanh di va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach va) OR (sach ha)) nang cao hoi. hieu van ((am thuc) or (nam thuc)) va thanh di va triet".
• Adding a wildcard symbol may retrieve word variants: su ((sach va) OR (sach ha)) nang cao hoi. hieu van ((am thuc) or (nam thuc)) va thanh di va triet*.