Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
su triet » su viet, su tien, ve triet
hieu va » lieu va, hieu qua
va cham » va chat, va tham
y nang » ky nang, ly nang, v nang
xac va » tac va, ac va, bac va
dan vi » doan vi, don vi, dan 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: toc sach y nang x hoi. hieu va cham ((xac va) or (duc va)) dan vi su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y nang x hoi. hieu va cham ((xac va) OR (duc va)) dan vi su triet.
• Adding a wildcard symbol may retrieve word variants: toc sach y nang x hoi. hieu va cham ((xac va) or (duc va)) dan vi su triet*.