Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
dang vat » dang van, dong vat, dang nhat
hieu van » hieu va, thien van, lieu va
hanh tai » thanh tai, hang tai, han tai
dang va » dang van, hang va, dung va
truc va » thuc va, thuc vat, trung va
tuc va » thuc va, tuc xa, duc va
cuc tu » cuc du, luc tu, duc tu

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 y ((dang va) or (dang vat)) hoi. hieu van nam ((tuc va) OR (truc va)) hanh tai cuc tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach y ((dang va) OR (dang vat)) hoi. hieu van nam ((tuc va) OR (truc va)) hanh tai cuc tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach y ((dang va) or (dang vat)) hoi. hieu van nam ((tuc va) OR (truc va)) hanh tai cuc tu".
• Adding a wildcard symbol may retrieve word variants: hoc sach y ((dang va) or (dang vat)) hoi. hieu van nam ((tuc va) OR (truc va)) hanh tai cuc tu*.