Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
va hanh » van hanh, va thanh, va danh
sach ly » sach y, sach lo, sach ty
hieu ve » hieu va, hieu van
su tien » su kien, su hien, tu tieng
hang ca » nang cao, hang tai, hang dau
va dan » ca dan, va dao, va dau
ve nam » he nam, va nam, le nam

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 ly ((hang ca) or (hang va)) hoi. hieu ve nam thuc ((va hanh) or (va dan)) va su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ly ((hang ca) OR (hang va)) hoi. hieu ve nam thuc ((va hanh) OR (va dan)) va su tien.
• Adding a wildcard symbol may retrieve word variants: toc sach ly ((hang ca) or (hang va)) hoi. hieu ve nam thuc ((va hanh) or (va dan)) va su tien*.