Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
va triet » va thiet, va trien, ve triet
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
cam duc » cam xuc, cao duc, pham duc
va hanh » van hanh, va thanh, va danh
hanh de » hanh ve, hanh kem
hieu va » hieu qua
sach 2 » sach y
de va » de van, te va, ke va

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach 2 ((nang xa) OR (nang ma)) hoi. ((hieu va) or (lieu va)) cam duc va hanh de va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach 2 ((nang xa) OR (nang ma)) hoi. ((hieu va) OR (lieu va)) cam duc va hanh de va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach 2 ((nang xa) OR (nang ma)) hoi. ((hieu va) or (lieu va)) cam duc va hanh de va triet".
• Adding a wildcard symbol may retrieve word variants: doc sach 2 ((nang xa) OR (nang ma)) hoi. ((hieu va) or (lieu va)) cam duc va hanh de va triet*.