Perhaps you should try some spelling variations:
duc manh » duc anh, duc minh, duc tan
sach ky » sac ky, sach ty, sach kem
nang ma » tang ma, sang ma, nang cao
qua cao » qua cac, qua ca, qua cai
anh dai » vanh dai, anh bai, anh dat
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: tu ((sach ky) OR (sach y)) nang ma hoi. hieu qua cao ((duc manh) or (suc manh)) anh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach y)) nang ma hoi. hieu qua cao ((duc manh) OR (suc manh)) anh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) OR (sach y)) nang ma hoi. hieu qua cao ((duc manh) or (suc manh)) anh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sach y)) nang ma hoi. hieu qua cao ((duc manh) or (suc manh)) anh dai cua tre*.