Perhaps you should try some spelling variations:
hieu quan » lieu quan, thien quan, lien quan
cau triet » cau trieu, su triet, cua triet
dang xay » dang van, van xay
van hanh » van thanh, ban hanh, van anh
cam duc » cam xuc, cao duc, pham duc
va danh » va dinh, va dan, va hanh
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
xay hoi » xa hoi, tay hoi, cay phoi
ty dang » ty xang, ky dang, ty hang
vi cau » va cau, ve cau, di cau

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 ty dang xay hoi. ((hieu quan) or (hieu qua)) cam duc ((van hanh) or (va danh)) vi cau triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty dang xay hoi. ((hieu quan) OR (hieu qua)) cam duc ((van hanh) OR (va danh)) vi cau triet.
• Adding a wildcard symbol may retrieve word variants: tu sach ty dang xay hoi. ((hieu quan) or (hieu qua)) cam duc ((van hanh) or (va danh)) vi cau triet*.