Perhaps you should try some spelling variations:
cac loai » cac bai, cac giai, cac dai
dinh hai » dinh thai, tinh hai, dinh ha
hai cua » thai cua, dai cua, hoi cua
va dinh » van dinh, va kinh, va tinh
cac lop » cac hop
sach ky » sac ky, sach ty, sach kem
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
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: thu ((sach ky) or (sach y)) nang x hoi. hieu va ((cac lop) OR (cac loai)) va dinh hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach ky) OR (sach y)) nang x hoi. hieu va ((cac lop) OR (cac loai)) va dinh hai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach ky) or (sach y)) nang x hoi. hieu va ((cac lop) OR (cac loai)) va dinh hai cua tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sach ky) or (sach y)) nang x hoi. hieu va ((cac lop) OR (cac loai)) va dinh hai cua tre*.