Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
tinh doi » trinh doc, trinh do, tinh hoc
sach ky » sac ky, sach y, sach ty
van cau » van dau, van hau, van chat
cau dan » cau danh, cac dan, ca dan
va tinh » may tinh
doi cua » dai cua, hoi cua
co hoi » co hoc
dan va » doan va, dan ca, ban va

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky nang ((co hoi) or (co loi)). hieu van cau dan va tinh doi cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang ((co hoi) OR (co loi)). hieu van cau dan va tinh doi cua vat.
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang ((co hoi) or (co loi)). hieu van cau dan va tinh doi cua vat*.