Perhaps you should try some spelling variations:
dang thanh » dong thanh, dang hanh, hoang thanh
dan thanh » danh thanh, ban thanh, van thanh
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
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: su sach ((ty nang) or (ty xang)) xa hoi. hieu van nam thuc ((dan thanh) OR (dang thanh)) de cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ty nang) OR (ty xang)) xa hoi. hieu van nam thuc ((dan thanh) OR (dang thanh)) de cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ty nang) or (ty xang)) xa hoi. hieu van nam thuc ((dan thanh) OR (dang thanh)) de cua te".
• Adding a wildcard symbol may retrieve word variants: su sach ((ty nang) or (ty xang)) xa hoi. hieu van nam thuc ((dan thanh) OR (dang thanh)) de cua te*.