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