Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
ban hang » ngan hang
chat luc » chat xuc, chat lua, nhan luc
ve chat » va chat, van chat
hieu ve » hieu va, hieu van
sang ma » tang ma, nang ma, sang tao
ky sang » ky nang, ky dang, ky tang
tu sach » su sach, te sach, tu cach
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: ((thu sach) or (tu sach)) ky sang ma hoi. hieu ve chat luc ((ban hanh) OR (ban hang)) vi cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (tu sach)) ky sang ma hoi. hieu ve chat luc ((ban hanh) OR (ban hang)) vi cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) or (tu sach)) ky sang ma hoi. hieu ve chat luc ((ban hanh) OR (ban hang)) vi cua vat".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) or (tu sach)) ky sang ma hoi. hieu ve chat luc ((ban hanh) OR (ban hang)) vi cua vat*.