Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
ve cham » va cham, ve chat, vu cham
su viet » so viet
xuc va » duc va, tuc va, luc va
x hoi » xa hoi, o hoi, x ho
vi su » va su, ve su, ki 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) or (toc sach)) ky nang x hoi. hieu ve cham ((xuc va) or (hoc va)) hanh vi su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (toc sach)) ky nang x hoi. hieu ve cham ((xuc va) OR (hoc va)) hanh vi su viet.
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (toc sach)) ky nang x hoi. hieu ve cham ((xuc va) or (hoc va)) hanh vi su viet*.