Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cay phoi » cap phoi, tay hoi, cay cho
sach ky » sac ky, sach y, sach ty
ky dang » ky nang, ky danh
xay hoi » xa hoi, tay hoi, gay thoi
thuc va » thuc vat, thuc dan, thuc day
cuu tre » cua tre, cau tren, cau treo
va dan » ca dan, va dao, va dau
dan va » doan va, dan ca, ban va
va cuu » va cau, va chu, va huu

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ky dang ((xay hoi) OR (cay phoi)). hieu ((ha nam) or (van nam)) thuc va dan va cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky dang ((xay hoi) OR (cay phoi)). hieu ((ha nam) OR (van nam)) thuc va dan va cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky dang ((xay hoi) OR (cay phoi)). hieu ((ha nam) or (van nam)) thuc va dan va cuu tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ky dang ((xay hoi) OR (cay phoi)). hieu ((ha nam) or (van nam)) thuc va dan va cuu tre*.