Perhaps you should try some spelling variations:
day thanh » dao thanh, dat thanh, da thanh
hieu van » hieu va, thien van, lieu va
thuc day » thuc dan, thuc vat
nam thuc » nam thuoc, am thuc, nam thu
nang mai » nang ma, nang tai, lang mai
mai hoi » mai khoi, dai hoi, lai hoi
co sach » bo sach, cuon sach, hoc sach
tu sach » thu sach, su sach, te sach
vi cau » va cau, ve cau, viet cau
di cau » da cau, diem cau

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) or (co sach)) ky nang mai hoi. hieu van nam thuc day thanh ((vi cau) or (di cau)) treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (co sach)) ky nang mai hoi. hieu van nam thuc day thanh ((vi cau) OR (di cau)) treo.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (co sach)) ky nang mai hoi. hieu van nam thuc day thanh ((vi cau) or (di cau)) treo*.