Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
nang xa » nang x, lang xa, nang ma
hieu va » hieu qua
cam duc » cam xuc, cao duc, pham duc
va hanh » van hanh, va thanh, va danh
sach 2 » sach y
2 nang » v nang
de van » le van, do van, ve van
de va » te va, ke va, le 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 hoi. ((hieu va) or (lieu va)) cam duc va hanh ((de va) OR (de van)) trien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach 2 nang xa hoi. ((hieu va) OR (lieu va)) cam duc va hanh ((de va) OR (de van)) trien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach 2 nang xa hoi. ((hieu va) or (lieu va)) cam duc va hanh ((de va) OR (de van)) trien".
• Adding a wildcard symbol may retrieve word variants: doc sach 2 nang xa hoi. ((hieu va) or (lieu va)) cam duc va hanh ((de va) OR (de van)) trien*.