Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
cac thuc » cach thuc, cac thu, can thuc
hieu va » lieu va, hieu qua
luan vi » quan vi, luan va, luan ve
va luan » vay luan, van luan, va quan
thuc va » thuc vat, thuc dan, thuc day
te sach » toc sach
sach ty » sach y, sach tu, sach thu
hieu ve » hieu van
mang xa » lang xa, mang may, dang xay
xang xa » lang xa, ang xa, dang xay
vi dau » vi dai, va dau, bi dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ty ((xang xa) or (mang xa)) hoi. ((hieu ve) OR (hieu va)) cac thuc va luan vi dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty ((xang xa) OR (mang xa)) hoi. ((hieu ve) OR (hieu va)) cac thuc va luan vi dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty ((xang xa) or (mang xa)) hoi. ((hieu ve) OR (hieu va)) cac thuc va luan vi dau tren".
• Adding a wildcard symbol may retrieve word variants: te sach ty ((xang xa) or (mang xa)) hoi. ((hieu ve) OR (hieu va)) cac thuc va luan vi dau tren*.