Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
va triet » va trien, ve triet, cua triet
van hanh » van thanh, ban hanh, van anh
cam duc » cam xuc, cao duc, pham duc
hanh de » hanh ve, hanh kem
hieu va » hieu qua
duc van » duc va, duc tan, duc manh
sach v » sach va, sach y, sach 2
nang o » nang co, nang ho, nang ro
v nang » va nang, vu nang, van nang
o hoi » co hoi, o hoc, o hai
thiet » thieu

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: thuoc sach v nang o hoi. ((hieu va) OR (lieu va)) cam duc van hanh de ((va triet) OR (va thiet))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuoc sach v nang o hoi. ((hieu va) or (lieu va)) cam duc van hanh de ((va triet) OR (va thiet))~".
• Adding a wildcard symbol may retrieve word variants: thuoc sach v nang o hoi. ((hieu va) or (lieu va)) cam duc van hanh de ((va triet) OR (va thiet))*.