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
cac dac » cac dan, cac dai, cac bac
va tinh » may tinh
tinh di » tinh doi, trinh di, tinh da
y xang » ty xang
xang o » lang o, tang o, dang o
dac va » duc va, day va, dat va
o hoi » co hoi, o hoc, o hai
di su » doi su, ki su, da su

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: ((te sach) OR (toc sach)) y xang o hoi. hieu va cac dac va tinh di su triet~.
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) y xang o hoi. hieu va cac dac va tinh di su triet*.