Perhaps you should try some spelling variations:
thanh dai » thanh hai, thanh tai, thanh dat
hieu van » hieu va, thien van, lieu va
nam duoc » nam thuoc, dat duoc, nam moc
ha thanh » va thanh, pham thanh, phan thanh
sach ky » sach y, sach ty, sach kem
da duoc » tao duoc, hoa duoc
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky
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) or (sac ky)) nang x hoi. hieu van ((nam duoc) OR (da duoc)) ha thanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sac ky)) nang x hoi. hieu van ((nam duoc) OR (da duoc)) ha thanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) or (sac ky)) nang x hoi. hieu van ((nam duoc) OR (da duoc)) ha thanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sac ky)) nang x hoi. hieu van ((nam duoc) OR (da duoc)) ha thanh dai cua tre*.