Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu ve » hieu va, hieu van
cac dac » cac dan, cac dai, cac bac
dac van » cac van, dao van, dam van
van anh » van thanh, tuan anh, van minh
v nang » va nang, vu nang, van nang
ve cac » va cac, vien cac
anh vi » hanh vi, anh va, anh ve
x hoi » xa hoi, o hoi, x ho
vi su » va su, ve su, ki su
kien* » bien*, vien*, tien*

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) or (cam nang)) x hoi. hieu ve cac dac van anh vi su kien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((v nang) OR (cam nang)) x hoi. hieu ve cac dac van anh vi su kien*.