Perhaps you should try some spelling variations:
hieu vien » hieu hien, thieu nien, hieu tieng
hieu viec » nhieu viec, hieu ve, sieu viet
cau tren » cu tren, dau tren, ca tren
van nang » van quang, van dong, van dung
van hanh » van thanh, ban hanh, van anh
thuc van » thuc vat, thuc dan, thuc va
cac thuc » cach thuc, cac thu, can thuc
hanh de » hanh ve, hanh kem
su sach » so sach, vu sach
de cau » ke cau, le cau, ve cau

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: su sach ((van nang) OR (van ban)) x ho. ((hieu vien) OR (hieu viec)) cac thuc van hanh de cau tren~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((van nang) or (van ban)) x ho. ((hieu vien) OR (hieu viec)) cac thuc van hanh de cau tren~".
• Adding a wildcard symbol may retrieve word variants: su sach ((van nang) or (van ban)) x ho. ((hieu vien) OR (hieu viec)) cac thuc van hanh de cau tren*.