Perhaps you should try some spelling variations:
hieu van » thien van, hieu ve
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
hieu va » hieu qua
han tai » hang tai, nhan tai, van tai
soc va » hoc va, loc va, doc va
va han » va phan, van han, va hanh
tai va » thai va, mai va, tri va
thiet » thieu

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang xa hoi. ((((hieu van) OR (hieu va))) or (lieu va)) cham soc va han tai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang xa hoi. ((((hieu van) OR (hieu va))) OR (lieu va)) cham soc va han tai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang xa hoi. ((((hieu van) OR (hieu va))) or (lieu va)) cham soc va han tai va thiet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang xa hoi. ((((hieu van) OR (hieu va))) or (lieu va)) cham soc va han tai va thiet*.