Perhaps you should try some spelling variations:
thanh hai » thanh phan, thanh hoa
hieu van » hieu va, thien van, lieu va
cua tre » cua te, cuu tre, cua triet
duc van » duc va, duc tan, duc manh
van cam » van nam, van lam, van cau
cam duc » cam xuc, cao duc, pham duc
ky dang » ky nang, ky danh
ky tang » ky nang, kho tang, ky trong
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 ((ky tang) or (ky dang)) xa hoi. hieu van cam duc van ((thanh hai) OR (thanh san)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sac ((ky tang) OR (ky dang)) xa hoi. hieu van cam duc van ((thanh hai) OR (thanh san)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sac ((ky tang) or (ky dang)) xa hoi. hieu van cam duc van ((thanh hai) OR (thanh san)) cua tre".
• Adding a wildcard symbol may retrieve word variants: su sac ((ky tang) or (ky dang)) xa hoi. hieu van cam duc van ((thanh hai) OR (thanh san)) cua tre*.