Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
nang xa » nang x, lang xa, nang ma
hieu ve » hieu va, hieu van
cac duc » cac du, cac dac, cac nuoc
cao duc » dao duc, cao suc, giao duc
vi cua » vai cua, di cua
cua su » qua 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 ty nang xa hoi. ((hieu ve) or (lieu va)) ((cac duc) or (cao duc)) van hanh vi cua su~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty nang xa hoi. ((hieu ve) OR (lieu va)) ((cac duc) OR (cao duc)) van hanh vi cua su.
• Adding a wildcard symbol may retrieve word variants: toc sach ty nang xa hoi. ((hieu ve) or (lieu va)) ((cac duc) or (cao duc)) van hanh vi cua su*.