Perhaps you should try some spelling variations:
cua triet » cua viet, su triet
doc sach » hoc sach, toc sach, nuoc sach
cac quoc » cac nuoc, cac cuoc, cao quoc
quoc ban » quoc bao, quoc lan, quoc quan
ban hanh » ban hang
va triet » va thiet, va trien, ve triet
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
lang xa » lang ha, dang xay, lang van
hieu va » lieu va, hieu qua

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ky ((nang ma) or (lang xa)) hoi. hieu va cac quoc ban hanh vi ((cua triet) OR (va triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ky ((nang ma) OR (lang xa)) hoi. hieu va cac quoc ban hanh vi ((cua triet) OR (va triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ky ((nang ma) or (lang xa)) hoi. hieu va cac quoc ban hanh vi ((cua triet) OR (va triet))".
• Adding a wildcard symbol may retrieve word variants: doc sach ky ((nang ma) or (lang xa)) hoi. hieu va cac quoc ban hanh vi ((cua triet) OR (va triet))*.