Perhaps you should try some spelling variations:
day thanh » dao thanh, dat thanh, da thanh
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, nam thu, nam tu
thanh de » hanh de, thanh ve, thanh do
ty nang » ky nang, ty hang, ly nang
de cua » le cua, te cua, dieu cua
cua te » cua tu

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