Perhaps you should try some spelling variations:
hieu quan » lieu quan, thien quan, lien quan
van hanh » van thanh, ban hanh, van anh
sach ky » sach y, sach ty, sach kem
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky
nam tu » nam thu, nam thuc
tu van » tu va
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) OR (sac ky)) nang x ho. ((hieu quan) or (hieu qua)) nam tu van hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sac ky)) nang x ho. ((hieu quan) OR (hieu qua)) nam tu van hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) OR (sac ky)) nang x ho. ((hieu quan) or (hieu qua)) nam tu van hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sac ky)) nang x ho. ((hieu quan) or (hieu qua)) nam tu van hanh di cua tre*.