Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thu nang » thi nang, thu hang, thu bang
thuc van » thuc vat, thuc dan, thuc hanh
sach thu » sach thue, sach thieu, sach tham
hanh di » hanh vi, hanh de, hang di
thuc va » thuc vat, thuc dan, thuc day
cua tre » cua te, cuu tre, cua triet
di cua » dai cua, doi cua, de cua
va cam » va cham, va cac, va cao
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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

• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach thu nang ((x hoi) OR (o hoi)). lieu va cam ((thuc van) OR (thuc va)) hanh di cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach thu nang ((x hoi) OR (o hoi)). lieu va cam ((thuc van) or (thuc va)) hanh di cua tre~".
• Adding a wildcard symbol may retrieve word variants: toc sach thu nang ((x hoi) OR (o hoi)). lieu va cam ((thuc van) or (thuc va)) hanh di cua tre*.