Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cay phoi » cap phoi, tay hoi, cay cho
thuc dan » thuc hanh, hoc dan, thuc vat
cau treo » cau theo, cau tren, cau triet
xay hoi » xa hoi, tay hoi, gay thoi
hieu va » lieu va, hieu qua
sach ty » sach y, sach tu, sach thu
thuc va » thuc vat, thuc day
ty dang » ty xang, ky dang, ty hang
dan va » doan va, dan ca, ban va
va cau » van cau, va cac, va dau
va nam » van nam, ha nam, va nay

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