Perhaps you should try some spelling variations:
dau thuc » dan thuc, dai thuc, dam thuc
tu sach » thu sach, su sach, te sach
thuc va » thuc vat, thuc dan, thuc day
xay hoi » tay hoi, cay phoi, gay thoi
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
te cua » tue cua, le cua, de cua
ve cua » le cua, de cua, ve cum
va dau » va dao
sach o » sach lo, sac o, sach y
o dang » xo dang, do dang, so dang

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

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