Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
dang xay » dang van, van xay
van hanh » van thanh, ban hanh, van anh
hanh dai » hanh tai, hanh dao, vanh dai
lang xa » lang ha, lang van
hieu ve » hieu va, hieu van
pham tu » phan tu, pham tai, pham duc
cua tu » cua tuc, cua su, cua cu

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 y ((lang xa) or (dang xay)) hoi. hieu ve ((pham thi) or (pham tu)) van hanh dai cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y ((lang xa) OR (dang xay)) hoi. hieu ve ((pham thi) OR (pham tu)) van hanh dai cua tu.
• Adding a wildcard symbol may retrieve word variants: toc sach y ((lang xa) or (dang xay)) hoi. hieu ve ((pham thi) or (pham tu)) van hanh dai cua tu*.