Perhaps you should try some spelling variations:
thuc toc » thac toc, thuc uoc, thuc thuc
va hanh » van hanh, va thanh, va danh
sach tu » sach thu, cach tu, sach ty
su sach » so sach, vu sach
nang xa » lang xa, nang ma, mang xa
hieu va » lieu va, hieu qua
toc va » hoc va, toc ta, tuc va
hai su » hai vu, hai so, tai su

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach tu ((nang xa) or (nang x)) hoi. hieu va thuc toc va hanh ((hai su) OR (lai su)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach tu ((nang xa) OR (nang x)) hoi. hieu va thuc toc va hanh ((hai su) OR (lai su)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach tu ((nang xa) or (nang x)) hoi. hieu va thuc toc va hanh ((hai su) OR (lai su)) triet".
• Adding a wildcard symbol may retrieve word variants: su sach tu ((nang xa) or (nang x)) hoi. hieu va thuc toc va hanh ((hai su) OR (lai su)) triet*.