Perhaps you should try some spelling variations:
van triet » va triet, van thiet, van trieu
hieu quan » hieu qua, lieu quan, thien quan
lang xa » dang xay, lang van
lang ha » long ha
sach ky » sac ky, sach y, sach ty
cau loc » hau loc, cau luc, cau long
cau hoc » cau hoi, cau hoa, cao hoc
su sach » so sach, vu sach
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va

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

• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((lang xa) OR (lang ha)) hoi. hieu quan ((cau loc) OR (cau hoc)) va dan vi van triet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((lang xa) or (lang ha)) hoi. hieu quan ((cau loc) OR (cau hoc)) va dan vi van triet~".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((lang xa) or (lang ha)) hoi. hieu quan ((cau loc) OR (cau hoc)) va dan vi van triet*.