Perhaps you should try some spelling variations:
nang doi » nang doc, nang noi, hang doi
thu sach » thuat sach, thuoc sach, thu hoach
dang xay » dang van, van xay
tu sach » su sach, te sach, tu cach
xa nang » da nang, va nang, xa nong
cac tac » cac toc, cac bac, cac dac
hieu va » lieu va, hieu qua
hieu ve » hieu van
xay hoi » xa hoi, tay hoi, cay phoi
ky dang » ky nang, ky danh
ca viet » va viet, co viet, hoa viet
tac xa » tuc xa, tac da
doi ca » doi cua, doi cay, duoi ca

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 dang xay hoi. ((hieu ve) OR (hieu va)) cac tac xa nang doi ca viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky dang xay hoi. ((hieu ve) OR (hieu va)) cac tac xa nang doi ca viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu sach)) ky dang xay hoi. ((hieu ve) OR (hieu va)) cac tac xa nang doi ca viet".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ky dang xay hoi. ((hieu ve) OR (hieu va)) cac tac xa nang doi ca viet*.