Perhaps you should try some spelling variations:
cam quoc » cac quoc, cao quoc, nam quoc
sang mai » sang ma, sang tai, lang mai
banh chi » danh cho, dinh chi, bao chi
quoc ban » quoc bao, quoc lan, quoc quan
tu sach » thu sach, su sach, te sach
banh di » danh di, xanh di, vanh dai
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
hieu va » hieu qua
mai hoi » mai khoi, dai hoi, lai hoi
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 ky sang mai hoi. ((lieu va) or (hieu va)) cam quoc ban ((banh di) OR (banh chi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky sang mai hoi. ((lieu va) OR (hieu va)) cam quoc ban ((banh di) OR (banh chi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky sang mai hoi. ((lieu va) or (hieu va)) cam quoc ban ((banh di) OR (banh chi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky sang mai hoi. ((lieu va) or (hieu va)) cam quoc ban ((banh di) OR (banh chi)) cua tre*.