Perhaps you should try some spelling variations:
ban thanh » ban hang
thai cua » than cua, tai cuc, tri cua
ban hanh » ban hang
hieu van » hieu va, thien van, lieu va
cua tre » cua te, cuu tre, cua triet
van cau » van dau, van hau, van chat
cau duc » cao duc, cau luc, chu duc
nang ma » tang ma, sang ma, nang cao
sai ky » sac ky
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu ((sai ky) or (cac ky)) nang ma hoi. hieu van cau duc ((ban thanh) OR (ban hanh)) thai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sai ky) OR (cac ky)) nang ma hoi. hieu van cau duc ((ban thanh) OR (ban hanh)) thai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sai ky) or (cac ky)) nang ma hoi. hieu van cau duc ((ban thanh) OR (ban hanh)) thai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sai ky) or (cac ky)) nang ma hoi. hieu van cau duc ((ban thanh) OR (ban hanh)) thai cua tre*.