Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
va trien » va truyen, va tuyen, va tieng
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 v » sach va, sach y, sach 2
v nang » va nang, vu nang, van nang
thiet » thieu

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 v nang xa hoi. ((hieu va) or (lieu va)) cam duc va hanh kem ((va trien) or (va thiet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach v nang xa hoi. ((hieu va) OR (lieu va)) cam duc va hanh kem ((va trien) OR (va thiet)).
• Adding a wildcard symbol may retrieve word variants: doc sach v nang xa hoi. ((hieu va) or (lieu va)) cam duc va hanh kem ((va trien) or (va thiet))*.