Perhaps you should try some spelling variations:
tinh dai » trinh dai, tinh da, tinh doi
tinh hai » tinh thai, tinh chat, trinh han
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
cau tu » dau tu, cau truc
tu may » tu ma, ty may, tu cay
x hoi » xa hoi, o hoi, x ho

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 nang x hoi. ((hieu ve) or (hieu qua)) cau tu may ((tinh dai) OR (tinh hai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x hoi. ((hieu ve) OR (hieu qua)) cau tu may ((tinh dai) OR (tinh hai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x hoi. ((hieu ve) or (hieu qua)) cau tu may ((tinh dai) OR (tinh hai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x hoi. ((hieu ve) or (hieu qua)) cau tu may ((tinh dai) OR (tinh hai)) cua tre*.