Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
hieu ve » hieu van
hieu va » lieu va, hieu qua
duc van » duc tan, duc manh, duc phan
vi cua » vai cua, di cua
cua tu » cua tuc, cua su, cua cu

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