Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
kho tang » cao tang
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
duc van » duc va, duc tan, duc manh
cac duc » cac du, cao duc, cac dac
hieu ve » hieu va, hieu van
ky tang » ky nang, ky dang, ky trong
ma hoi » mai hoi, xa hoi, ma hoa
ve cac » va cac, vien cac
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) OR (kho tang)) ma hoi. hieu ve cac duc van hanh vi cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thuoc sach)) ((ky tang) OR (kho tang)) ma hoi. hieu ve cac duc van hanh vi cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thuoc sach)) ((ky tang) OR (kho tang)) ma hoi. hieu ve cac duc van hanh vi cua vat".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thuoc sach)) ((ky tang) OR (kho tang)) ma hoi. hieu ve cac duc van hanh vi cua vat*.