Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
tu sach » thu sach, su sach, te sach
doi cua » dai cua, hoi cua
tac ban » tai ban, cac ban, tao ban
cac tac » cac toc, cac bac, cac dac
hieu ve » hieu va, hieu van
sach ky » sac ky, sach y, sach ty
tay hoi » tay ho, tao hoi, tay thai
xay hoi » xa hoi, cay phoi, gay thoi
ky dang » ky nang, ky danh
ve cac » va cac, vien cac
di cua » dai cua, de cua, do 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 ky dang ((xay hoi) OR (tay hoi)). hieu ve cac tac ban thanh ((di cua) or (doi cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky dang ((xay hoi) OR (tay hoi)). hieu ve cac tac ban thanh ((di cua) OR (doi cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky dang ((xay hoi) OR (tay hoi)). hieu ve cac tac ban thanh ((di cua) or (doi cua)) tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky dang ((xay hoi) OR (tay hoi)). hieu ve cac tac ban thanh ((di cua) or (doi cua)) tre*.