Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
qua pham » quan pham, quy pham, qua cham
van hanh » van thanh, ban hanh, van anh
ky tang » ky nang, kho tang, ky trong
ky dang » ky nang, ky danh
van hoi » van hoa, van hoc, van hoe
va hanh » va thanh, va danh, ban hanh
de cua » le cua, te cua, dieu 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 ((ky tang) OR (ky dang)) van hoi. hieu qua pham duc ((va hanh) or (van hanh)) de cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((ky tang) OR (ky dang)) van hoi. hieu qua pham duc ((va hanh) OR (van hanh)) de cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((ky tang) OR (ky dang)) van hoi. hieu qua pham duc ((va hanh) or (van hanh)) de cua te".
• Adding a wildcard symbol may retrieve word variants: toc sach ((ky tang) OR (ky dang)) van hoi. hieu qua pham duc ((va hanh) or (van hanh)) de cua te*.