Perhaps you should try some spelling variations:
day thanh » dao thanh, dat thanh, da thanh
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, nam thu, nam tu
thanh do » thanh de, thanh pho, thanh hoa
ty nang » ky nang, ty xang, ty hang
nang xa » nang x, lang xa, nang ma
cua tre » cua te, cuu tre, cua triet
do cua » doi cua, co cua, de cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) OR (doc sach)) ty nang xa hoi. hieu van ((nam thuc) or (am thuc)) day thanh do cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ty nang xa hoi. hieu van ((nam thuc) OR (am thuc)) day thanh do cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) ty nang xa hoi. hieu van ((nam thuc) or (am thuc)) day thanh do cua tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (doc sach)) ty nang xa hoi. hieu van ((nam thuc) or (am thuc)) day thanh do cua tre*.