Perhaps you should try some spelling variations:
sach kem » hanh kem
hieu van » hieu va, thien van, lieu va
cua viet » ca viet, cua vat, cua dieu
nang xa » nang x, lang xa, nang ma
van cau » van dau, van hau, van chat
truc va » thuc va, thuc vat, trung va
va xanh » va danh, va hanh, va anh
xanh di » danh di, vanh dai, xanh tai

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: thu ((sach kem) OR (sach y)) nang xa hoi. hieu van cau truc va xanh di ((cua viet) OR (hoa viet))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach kem) or (sach y)) nang xa hoi. hieu van cau truc va xanh di ((cua viet) OR (hoa viet))~".
• Adding a wildcard symbol may retrieve word variants: thu ((sach kem) or (sach y)) nang xa hoi. hieu van cau truc va xanh di ((cua viet) OR (hoa viet))*.