Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
van chat » cao chat
van tham » van thanh, van tuan, van tai
van nang » van quang, van ban, van dong
thuc va » thuc vat, thuc dan, thuc day
dan sai » danh sai, doan sai, dan tai
sai cua » dai cua, hai cua, lai cua
v nang » va nang, vu nang, voi nang
va dan » ca dan, va dao, va dau
cua te » cua tu
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach ((v nang) OR (van nang)) o hoi. thien ((van tham) or (van chat)) thuc va dan sai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ((v nang) OR (van nang)) o hoi. thien ((van tham) OR (van chat)) thuc va dan sai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ((v nang) OR (van nang)) o hoi. thien ((van tham) or (van chat)) thuc va dan sai cua te".
• Adding a wildcard symbol may retrieve word variants: hoc sach ((v nang) OR (van nang)) o hoi. thien ((van tham) or (van chat)) thuc va dan sai cua te*.