Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
thu sach » tu sach, thuat sach, thu hoach
cao hoi » cau hoi, co hoi, cao hoc
hieu va » lieu va, hieu qua
cac dat » cai dat, cac dai, cac dac
va tinh » may tinh
tinh va » tich va, trinh van, trinh vat
va cua » va chua, via cua, ca cua

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) OR (thuoc sach)) ky nang cao hoi. hieu va ((cac dat) or (cac dan)) va tinh va cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (thuoc sach)) ky nang cao hoi. hieu va ((cac dat) OR (cac dan)) va tinh va cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) OR (thuoc sach)) ky nang cao hoi. hieu va ((cac dat) or (cac dan)) va tinh va cua vat".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) OR (thuoc sach)) ky nang cao hoi. hieu va ((cac dat) or (cac dan)) va tinh va cua vat*.