Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
cua viet » ca viet, hoa viet, cua vat
buoc ban » quoc ban, buon ban, duoc ban
cac buoc » cac nuoc, cac cuoc, cac quoc
vien cac » vien bach, vien dai, vien da
nang ma » tang ma, sang ma, nang cao
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, mang xa
hanh di » hanh de, hang di, danh di
so sach » so sanh, bo sach, co sach

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky ((nang xa) or (nang ma)) hoi. hieu vien cac buoc ban ((hanh di) or (hanh vi)) cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky ((nang xa) OR (nang ma)) hoi. hieu vien cac buoc ban ((hanh di) OR (hanh vi)) cua viet.
• Adding a wildcard symbol may retrieve word variants: so sach ky ((nang xa) or (nang ma)) hoi. hieu vien cac buoc ban ((hanh di) or (hanh vi)) cua viet*.