Perhaps you should try some spelling variations:
thien van » thi van
van chat » cao chat
han tai » hang tai, nhan tai, van tai
sach ky » sac ky, sach y, sach ty
tu sach » thu sach, su sach, te sach
nang xa » nang x, nang ma, mang xa
lang xa » lang ha, dang xay, lang van
soc va » hoc va, loc va, goc va
doc va » duoc va, hoc va, duc va
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) or (lang xa)) hoi. thien van chat ((soc va) OR (doc va)) han tai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang xa) OR (lang xa)) hoi. thien van chat ((soc va) OR (doc va)) han tai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang xa) or (lang xa)) hoi. thien van chat ((soc va) OR (doc va)) han tai va thiet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang xa) or (lang xa)) hoi. thien van chat ((soc va) OR (doc va)) han tai va thiet*.