Perhaps you should try some spelling variations:
thien quan » trien quang, lien quan, thien van
hieu quan » lieu quan, lien quan, hieu luat
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
va hang » van hang, va nang, va lang
hang di » hang doi, hang vi, hang dien
cua tre » cua te, cuu tre, cua triet
nam tu » nam thu, nam thuc
di cua » dai cua, doi cua, de cua

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 ho. ((((hieu quan) OR (thien quan))) or (hieu qua)) nam tu va hang di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x ho. ((((hieu quan) OR (thien quan))) OR (hieu qua)) nam tu va hang di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x ho. ((((hieu quan) OR (thien quan))) or (hieu qua)) nam tu va hang di cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x ho. ((((hieu quan) OR (thien quan))) or (hieu qua)) nam tu va hang di cua tre*.