Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
su triet » su viet, su tien, ve triet
nang xa » nang x, lang xa, nang ma
dam tu » nam tu, tam tu, dam thuc
cam tu » cam thu, nam tu, tam tu
vi su » va su, ve su, ki su

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) or (hoc sinh)) ky nang xa hoi. hieu van ((dam tu) OR (cam tu)) van hanh vi su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sinh)) ky nang xa hoi. hieu van ((dam tu) OR (cam tu)) van hanh vi su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc sinh)) ky nang xa hoi. hieu van ((dam tu) OR (cam tu)) van hanh vi su triet".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sinh)) ky nang xa hoi. hieu van ((dam tu) OR (cam tu)) van hanh vi su triet*.