Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
duc manh » suc manh, duc anh, duc minh
va triet » va thiet, va trien, ve triet
nang xa » nang x, lang xa, nang ma
hieu va » hieu qua
duc van » duc va, duc tan, duc phan
sach v » sach va, sach y, sach 2
v nang » va nang, vu nang, van nang
kem va » kiem va, kiem van

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

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