Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
nang cho » nang chon, ngang cho, nang cao
van hanh » van thanh, ban hanh, van ban
cac vung » cac ung, cac chung, cach dung
sach tu » sach thu, cach tu, sach ty
van anh » van thanh, tuan anh, van minh
cua cau » cua cac, cua chu, cua cay
cac vuc » cac nuoc, cac cuoc, cac quoc
cho hoc » co hoc, khoa hoc
tu nang » tru nang, tu nong, tu nano
vi cua » vai cua, di cua

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: doc sach tu nang cho hoc. hieu qua ((cac vuc) OR (cac vung)) ((van hanh) OR (van anh)) vi cua cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach tu nang cho hoc. hieu qua ((cac vuc) OR (cac vung)) ((van hanh) or (van anh)) vi cua cau~".
• Adding a wildcard symbol may retrieve word variants: doc sach tu nang cho hoc. hieu qua ((cac vuc) OR (cac vung)) ((van hanh) or (van anh)) vi cua cau*.