Perhaps you should try some spelling variations:
thanh dai » thanh hai, thanh tai, thanh dat
ban thanh » ban hanh, ban hang
kho tang » cao tang
hieu van » hieu va, thien van, lieu va
cua tre » cua te, cuu tre, cua triet
cac dac » cac dan, cac dai, cac bac
cac duc » cac du, cao duc, cac nuoc
ma hoi » mai hoi, xa hoi, ma hoa
su sac » su sach, su cac, su xac

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

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