Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
sach van » sach han, sach va, bach van
van nang » van quang, van ban, van dong
vien cac » vien bach, vien dai, vien da
cac thuc » cach thuc, cac thu, can thuc
van hanh » van thanh, ban hanh, van ban
cau tren » cu tren, dau tren, ca tren
su sach » so sach, vu sach
van anh » van thanh, tuan anh, van minh
de cau » ke cau, le cau, ve cau

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

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