Perhaps you should try some spelling variations:
ve triet » va trien
nang mai » nang ma, lang mai, nang cai
su triet » su viet, su tien
nang tai » hang tai, tang tai, sang tai
van hanh » van thanh, ban hanh, van anh
luc van » luoc van, luu van, duc van
hanh ki » hanh vi, hanh ky, hanh kien
tu sach » thu sach, su sach, te sach
cac luc » cau luc, coc luc, cac nuoc
sach vu » sach va, sach tu, sach uu
hieu va » lieu va, hieu qua

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 ((nang mai) or (nang tai)) hoi. hieu va cac luc van hanh ki ((su triet) or (ve triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach vu ((nang mai) OR (nang tai)) hoi. hieu va cac luc van hanh ki ((su triet) OR (ve triet)).
• Adding a wildcard symbol may retrieve word variants: tu sach vu ((nang mai) or (nang tai)) hoi. hieu va cac luc van hanh ki ((su triet) or (ve triet))*.