Perhaps you should try some spelling variations:
ha thanh » va thanh, pham thanh, phan thanh
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
su sach » so sach, vu sach
hieu ve » hieu van
cac tac » cac toc, cac bac, cac dac
tac ha » bac ha, tac da, tac xa
x hoi » xa hoi, o hoi, x ho
vi su » va su, ve su, oi su
ki su » ky su

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang x hoi. ((hieu ve) OR (hieu va)) cac tac ha thanh ((vi su) OR (ki su)) triet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang x hoi. ((hieu ve) OR (hieu va)) cac tac ha thanh ((vi su) or (ki su)) triet~".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang x hoi. ((hieu ve) OR (hieu va)) cac tac ha thanh ((vi su) or (ki su)) triet*.