Perhaps you should try some spelling variations:
dieu hien » dieu khien, dieu kien, bieu hien
hieu hien » bieu hien, chieu chien, dieu khien
doan vi » doan va, don vi, doan thi
cach tu » cach thuc
sach ky » sac ky, sach y, sach ty
su sach » so sach, vu sach
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
cua tre » cua te, cuu tre, cua triet
dan vi » don vi, dan va, gan vi

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 lang xa hoi. ((hieu hien) OR (dieu hien)) cach tu va ((dan vi) or (doan vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky lang xa hoi. ((hieu hien) OR (dieu hien)) cach tu va ((dan vi) OR (doan vi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky lang xa hoi. ((hieu hien) OR (dieu hien)) cach tu va ((dan vi) or (doan vi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky lang xa hoi. ((hieu hien) OR (dieu hien)) cach tu va ((dan vi) or (doan vi)) cua tre*.