Perhaps you should try some spelling variations:
phan tai » pham tai, nhan tai, phan thi
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
ve cham » va cham, ve chat, vu cham
lang xa » lang ha, dang xay, lang van
luc va » duc va, loc va
tuc va » thuc va, truc va, tuc xa
tai va » thai va, mai va, tri va
thiet » thieu

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 y ((lang xa) OR (nang x)) hoi. hieu ve cham ((luc va) OR (tuc va)) phan tai va thiet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y ((lang xa) or (nang x)) hoi. hieu ve cham ((luc va) OR (tuc va)) phan tai va thiet~".
• Adding a wildcard symbol may retrieve word variants: su sach y ((lang xa) or (nang x)) hoi. hieu ve cham ((luc va) OR (tuc va)) phan tai va thiet*.