Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
dang xay » dang van, van xay
va hanh » van hanh, va thanh, va danh
cau duc » cao duc, cau luc, chu duc
sach ky » sac ky, sach y, sach ty
tu sach » thu sach, su sach, te sach
nang xa » nang x, lang xa, nang ma
van cau » van dau, van hau, van chat
hai su » lai su, hai so, tai su
hai vu » hai va

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 (dang xay)) hoi. hieu van cau duc va hanh ((hai su) OR (hai vu)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang xa) OR (dang xay)) hoi. hieu van cau duc va hanh ((hai su) OR (hai vu)) triet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang xa) or (dang xay)) hoi. hieu van cau duc va hanh ((hai su) OR (hai vu)) triet*".