Perhaps you should try some spelling variations:
kho tang » cao tang
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
ky tang » ky nang, ky dang, ky trong
van cau » van dau, van hau, van chat
truc va » thuc va, thuc vat, trung va
va tinh » may tinh
tinh va » tich va, trinh van, trinh vat
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ((ky tang) OR (kho tang)) xa hoi. hieu van cau truc va tinh va ((cua tre) or (cua vat))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ky tang) OR (kho tang)) xa hoi. hieu van cau truc va tinh va ((cua tre) OR (cua vat))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ky tang) OR (kho tang)) xa hoi. hieu van cau truc va tinh va ((cua tre) or (cua vat))*".