Perhaps you should try some spelling variations:
sach ky » sach y, sach ty, sach kem
cao hoi » cau hoi, co hoi, cao hoc
hieu ve » hieu va, hieu van
luu tre » luu tru, cuu tre, luy tre
sac ky » cac ky, sai ky
ve cac » va cac, vien cac
luc va » tuc va, loc va
vi luu » vi lua

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

• Performing a fuzzy search may retrieve terms with similar spellings: te ((sach ky) OR (sac ky)) nang cao hoi. hieu ve cac ((duc va) or (luc va)) hanh vi luu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach ky) OR (sac ky)) nang cao hoi. hieu ve cac ((duc va) OR (luc va)) hanh vi luu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach ky) OR (sac ky)) nang cao hoi. hieu ve cac ((duc va) or (luc va)) hanh vi luu tre".
• Adding a wildcard symbol may retrieve word variants: te ((sach ky) OR (sac ky)) nang cao hoi. hieu ve cac ((duc va) or (luc va)) hanh vi luu tre*.