Perhaps you should try some spelling variations:
thanh doi » thanh loi, thanh moi, thanh do
dan thanh » dang thanh, danh thanh, ban thanh
hoc sach » hoc sinh, hoc cac, hoc anh
thuc dan » thuc hanh, hoc dan, thuc vat
cam thuc » am thuc, nam thuc, cam thu
hieu van » thien van, lieu va, hieu ve
tay lang » tai lang, tay tang, tay quang
lang xa » lang ha, dang xay, lang van
hieu va » lieu va, hieu qua
so sanh » do sanh
doi qua » doi cua, hoi qua, doi quy

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

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