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