Perhaps you should try some spelling variations:
dieu hien » dieu khien, dieu kien, bieu hien
hieu vien » hieu viec, thieu nien, hieu tieng
hieu hien » bieu hien, chieu chien, dieu khien
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cac bac » cac bai, cac ban, cac cach
cuu tre » cua tre, cau tren, cau treo
bac va » ban va, bac ha, bao va
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va
vi cuu » vi luu, vinh cuu
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang x hoi. ((hieu vien) or (((hieu hien) OR (dieu hien)))) cac bac va dan vi cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x hoi. ((hieu vien) OR (((hieu hien) OR (dieu hien)))) cac bac va dan vi cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x hoi. ((hieu vien) or (((hieu hien) OR (dieu hien)))) cac bac va dan vi cuu tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x hoi. ((hieu vien) or (((hieu hien) OR (dieu hien)))) cac bac va dan vi cuu tre*.