Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
nay thuc » nam thuc, cay thuc, day thuc
toc sac » toc sach, toc san, hoc sach
dan vai » dan va, dan tai, dan vat
thuc va » thuc vat, thuc dan, thuc day
hieu va » lieu va, hieu qua
lang ha » long ha
lang xa » dang xay, lang van
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky
va nay » va ngay, va cay
va dan » ca dan, va dao, va dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sac ky ((lang xa) OR (lang ha)) hoi. hieu va nay thuc va dan vai ((dau tren) or (cua tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sac ky ((lang xa) OR (lang ha)) hoi. hieu va nay thuc va dan vai ((dau tren) OR (cua tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sac ky ((lang xa) OR (lang ha)) hoi. hieu va nay thuc va dan vai ((dau tren) or (cua tre))".
• Adding a wildcard symbol may retrieve word variants: toc sac ky ((lang xa) OR (lang ha)) hoi. hieu va nay thuc va dan vai ((dau tren) or (cua tre))*.