Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
van hanh » van thanh, ban hanh, van anh
sach ky » sac ky, sach ty, sach kem
cac toc » cac toi, cac nuoc, cac thoi
toc van » hoc van, toc san, tac van
su tien » su kien, su hien, tu tieng
x hoi » xa hoi, o hoi, 5 hoi
vi su » va su, ve su, ki su

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

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach ky) OR (sach y)) nang ((x hoi) or (x ho)). hieu vien cac toc van hanh vi su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sach y)) nang ((x hoi) OR (x ho)). hieu vien cac toc van hanh vi su tien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) OR (sach y)) nang ((x hoi) or (x ho)). hieu vien cac toc van hanh vi su tien".
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) OR (sach y)) nang ((x hoi) or (x ho)). hieu vien cac toc van hanh vi su tien*.