Perhaps you should try some spelling variations:
vat hanh » vat thanh, van hanh, va hanh
su sach » so sach, vu sach
hieu ve » hieu van
hieu va » lieu va, hieu qua
y nang » ky nang, ly nang, v nang
di cuu » di cau, dinh cuu
di cua » dai cua, doi cua, de cua
x hoi » xa hoi, o hoi, x ho
thuc » thu

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 y nang x hoi. ((hieu ve) OR (hieu va)) am thuc vat hanh ((di cuu) or (di cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y nang x hoi. ((hieu ve) OR (hieu va)) am thuc vat hanh ((di cuu) OR (di cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y nang x hoi. ((hieu ve) OR (hieu va)) am thuc vat hanh ((di cuu) or (di cua)) tre".
• Adding a wildcard symbol may retrieve word variants: su sach y nang x hoi. ((hieu ve) OR (hieu va)) am thuc vat hanh ((di cuu) or (di cua)) tre*.