Perhaps you should try some spelling variations:
nay thuc » nam thuc, cay thuc, day thuc
cau tren » cu tren, dau tren, ca tren
toc sac » toc sach, toc san, hoc sach
dao vai » dao van, dao va, dao bai
thuc va » thuc vat, thuc dan, thuc day
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
ky tang » ky nang, ky dang, kho tang
ky lang » ky nang, ky dang, tay lang
va dao » ca dao
va nay » va ngay, va cay

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