Perhaps you should try some spelling variations:
thanh dai » thanh hai, thanh tai, thanh dat
dan thanh » dang thanh, danh thanh, ban thanh
hieu van » hieu va, thien van, lieu va
cam thuc » am thuc, cam thu, can thuc
tay lang » tai lang, tay tang, tay quang
nam thuc » nam thuoc, am thuc, nam thu
so sach » bo sach, co sach, hoc sach
lang xa » lang ha, dang xay, lang van
so sanh » do sanh
cua su » qua su

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((so sach) or (so sanh)) tay lang xa hoi. hieu van ((cam thuc) OR (nam thuc)) dan thanh dai cua su~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((so sach) OR (so sanh)) tay lang xa hoi. hieu van ((cam thuc) OR (nam thuc)) dan thanh dai cua su.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((so sach) or (so sanh)) tay lang xa hoi. hieu van ((cam thuc) OR (nam thuc)) dan thanh dai cua su".
• Adding a wildcard symbol may retrieve word variants: ((so sach) or (so sanh)) tay lang xa hoi. hieu van ((cam thuc) OR (nam thuc)) dan thanh dai cua su*.