Perhaps you should try some spelling variations:
su sach » so sach, vu sach
hanh ki » hanh vi, hanh ky, hanh kien
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va, hieu van
ty tang » tay tang, ty xang, ty hang
su viet » so viet
ve cau » ke cau, va cau, ve cac
ma hoi » mai hoi, xa hoi, me hoi
luc va » tuc va, loc va
ki su » ky 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 ty tang ((ma hoi) or (ma hoa)). hieu ve cau ((luc va) or (duc va)) hanh ki su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty tang ((ma hoi) OR (ma hoa)). hieu ve cau ((luc va) OR (duc va)) hanh ki su viet.
• Adding a wildcard symbol may retrieve word variants: su sach ty tang ((ma hoi) or (ma hoa)). hieu ve cau ((luc va) or (duc va)) hanh ki su viet*.