Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hanh dai » hanh tai, hanh dao, vanh dai
huu thuc » cuu thuc, huu phuc, huu thu
hau thuc » ha thuc, mau thuc, khau thuoc
hieu van » hieu va, thien van, lieu va
nang ma » tang ma, sang ma, nang cao
su sach » so sach, vu sach
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa

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) or (su sach)) ky nang ma hoi. hieu van ((hau thuc) OR (huu thuc)) va hanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (su sach)) ky nang ma hoi. hieu van ((hau thuc) OR (huu thuc)) va hanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) or (su sach)) ky nang ma hoi. hieu van ((hau thuc) OR (huu thuc)) va hanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) or (su sach)) ky nang ma hoi. hieu van ((hau thuc) OR (huu thuc)) va hanh dai cua tre*.