Perhaps you should try some spelling variations:
cua triet » cua viet, su triet
va triet » va thiet, va trien, ve triet
toc sach » hoc sach, doc sach, thuoc sach
cac duc » cac du, cao duc, cac dac
tinh di » tinh doi, trinh di, tinh da
va tinh » may tinh
hieu va » lieu va, hieu qua
xang o » lang o, tang o, dang o
y xang » ty xang
o hoi » co hoi, o hoc, o hai

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) or (toc sach)) y xang o hoi. hieu va cac duc va tinh di ((cua triet) OR (va triet))~.
• 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 duc va tinh di ((cua triet) OR (va triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) y xang o hoi. hieu va cac duc va tinh di ((cua triet) OR (va triet))".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) y xang o hoi. hieu va cac duc va tinh di ((cua triet) OR (va triet))*.