Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
hanh ki » hanh vi, hanh ky, hanh kien
luc van » luoc van, luu van, duc van
vuc van » duc van, thuc van, chuc van
tu sach » thu sach, su sach, te sach
sach tu » sach thu, cach tu, sach ty
dai hoi » dai hoc, dai hai, dai moi
mai hoi » mai khoi, lai hoi, mai doi
tu nang » tru nang, tu nong, tu nano
hieu va » lieu va, hieu qua
va cam » va cham, va cac, va cao
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 tu nang ((mai hoi) or (dai hoi)). hieu va cam ((vuc van) or (luc van)) hanh ki su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach tu nang ((mai hoi) OR (dai hoi)). hieu va cam ((vuc van) OR (luc van)) hanh ki su triet.
• Adding a wildcard symbol may retrieve word variants: tu sach tu nang ((mai hoi) or (dai hoi)). hieu va cam ((vuc van) or (luc van)) hanh ki su triet*.