Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
van thanh » ban thanh, van tuan
van hanh » ban hanh, van anh, van ban
tu sach » thu sach, su sach, te sach
cac duc » cac du, cao duc, cac dac
hieu ve » hieu va, hieu van
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
ve cac » va cac, vien cac
ma hoi » mai hoi, xa hoi, ma hoa
vi cua » vai cua, di cua

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

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