Perhaps you should try some spelling variations:
dat khanh » van khanh, duy khanh
dat thanh » dao thanh, dang thanh, danh thanh
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
so sach » so sanh, bo sach, co sach
cuu tre » cua tre, cau tren, cau treo
vi cuu » vi luu, vinh cuu
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) or (so sach)) ky nang x hoi. hieu van nam thuc ((dat thanh) OR (dat khanh)) vi cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (so sach)) ky nang x hoi. hieu van nam thuc ((dat thanh) OR (dat khanh)) vi cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (so sach)) ky nang x hoi. hieu van nam thuc ((dat thanh) OR (dat khanh)) vi cuu tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (so sach)) ky nang x hoi. hieu van nam thuc ((dat thanh) OR (dat khanh)) vi cuu tre*.