Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
su triet » su viet, su tien, ve triet
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
va hang » van hang, va nang, va lang
hang vi » hang va, hanh vi, hang di
ca viet » va viet, co viet, hoa viet
y nang » ky nang, ly nang, v nang

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: toc sach y nang ma hoa. hieu va cac nuoc va hang vi ((ca viet) OR (su triet))~.
• Adding a wildcard symbol may retrieve word variants: toc sach y nang ma hoa. hieu va cac nuoc va hang vi ((ca viet) or (su triet))*.