Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
dua ban » dia ban, cua ban, qua ban
duc ban » duc tan, duc van, duc man
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
hieu ve » hieu van
sach 2 » sach y
nang o » nang co, nang ho, nang ro
2 nang » v nang
o hoi » co hoi, o hoc, o hai
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: tu sach 2 nang o hoi. ((hieu ve) OR (hieu va)) cac ((duc ban) or (dua ban)) hanh vi su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach 2 nang o hoi. ((hieu ve) OR (hieu va)) cac ((duc ban) OR (dua ban)) hanh vi su triet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach 2 nang o hoi. ((hieu ve) OR (hieu va)) cac ((duc ban) or (dua ban)) hanh vi su triet*".