Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
nang xa » nang x, lang xa, nang ma
qua cac » cua cac
cac tuc » cac toc, cac tu, cac tac
va hanh » va thanh, va danh, ban hanh
vi cua » vai cua, di cua
cua te » cua tu

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 ((nang xa) or (nang cao)) hoi. hieu qua cac tuc ((va hanh) OR (van hanh)) vi cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y ((nang xa) OR (nang cao)) hoi. hieu qua cac tuc ((va hanh) OR (van hanh)) vi cua te*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach y ((nang xa) or (nang cao)) hoi. hieu qua cac tuc ((va hanh) OR (van hanh)) vi cua te*".