Perhaps you should try some spelling variations:
thien van » thi van
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
thuc dan » thuc hanh, hoc dan, thuc vat
thuc va » thuc vat, thuc day
van dam » van nam, van dao, van dau
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
cuu tre » cua tre, cau tren, cau treo
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) OR (doc sach)) ky lang xa hoi. thien van dam ((thuc va) or (thuc dan)) dan va cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ky lang xa hoi. thien van dam ((thuc va) OR (thuc dan)) dan va cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) ky lang xa hoi. thien van dam ((thuc va) or (thuc dan)) dan va cuu tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (doc sach)) ky lang xa hoi. thien van dam ((thuc va) or (thuc dan)) dan va cuu tre*.