Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
lang mai » lang dai, lang hai, lang man
hanh ki » hanh vi, hanh ky, hanh kien
duc van » duc va, duc tan, duc manh
luc van » luoc van, luu van, luc va
tu sach » thu sach, su sach, te sach
sach vu » sach va, sach tu, sach uu
hieu va » hieu qua
mai hoi » mai khoi, dai hoi, lai hoi
vu lang » va lang, vu dang, cu lang
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 vu lang mai hoi. ((hieu va) or (lieu va)) cam ((luc van) OR (duc van)) hanh ki su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach vu lang mai hoi. ((hieu va) OR (lieu va)) cam ((luc van) OR (duc van)) hanh ki su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach vu lang mai hoi. ((hieu va) or (lieu va)) cam ((luc van) OR (duc van)) hanh ki su triet".
• Adding a wildcard symbol may retrieve word variants: tu sach vu lang mai hoi. ((hieu va) or (lieu va)) cam ((luc van) OR (duc van)) hanh ki su triet*.