Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
thu sach » thuat sach, thuoc sach, thu hoach
hieu van » hieu va, thien van, lieu va
tu sach » su sach, te sach, tu cach
dua ban » dia ban, cua ban, qua ban
hai cua » thai cua, dai cua, hoi cua
vai cua » dai cua, lai cua, bai cua
van cau » van dau, van hau, van chat
cau dua » cau qua, cau cua, ca dua
sang ma » tang ma, nang ma, sang tao
ky sang » ky nang, ky dang, ky tang

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 (thu sach)) ky sang ma hoa. hieu van cau dua ban thanh ((vai cua) or (hai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky sang ma hoa. hieu van cau dua ban thanh ((vai cua) OR (hai cua)) tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (thu sach)) ky sang ma hoa. hieu van cau dua ban thanh ((vai cua) or (hai cua)) tre*".