Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
thuc dan » thuc hanh, hoc dan, thuc vat
sach thu » sach thue, sach thieu, sach tham
thuc va » thuc vat, thuc day
cua tre » cua te, cuu tre, cua triet
sach ty » sach y, sach tu, xach tay
lang xa » lang ha, dang xay, lang van
dan va » doan va, dan ca, ban va
va cua » va chua, via cua, ca cua
van am » van nam, van lam, van dam

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