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

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