Perhaps you should try some spelling variations:
va triet » va thiet, va trien, ve triet
sach thu » sach thue, sach thieu, sach tham
hanh dai » hanh tai, hanh dao, vanh dai
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
hieu ve » hieu va, hieu van
ca viet » va viet, co viet, hoa viet
sach ty » sach y, sach tu, xach tay
nang o » nang co, nang ho, nang ro
ve am » va am
o hoi » co hoi, o hoc, o hai

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ty) OR (sach thu)) nang o hoi. hieu ve am thuc va hanh dai ((va triet) OR (ca viet))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ty) OR (sach thu)) nang o hoi. hieu ve am thuc va hanh dai ((va triet) or (ca viet))~".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ty) OR (sach thu)) nang o hoi. hieu ve am thuc va hanh dai ((va triet) or (ca viet))*.