Perhaps you should try some spelling variations:
giai duc » giao duc, gia duc, giap duc
van hanh » van thanh, ban hanh, van anh
sach le » sach de, sach lo, sach kem
cach le » cach de, cach ben, cach lam
xay hoi » xa hoi, tay hoi, cay phoi
hieu va » lieu va, hieu qua
duc van » duc va, duc tan, duc manh
cac le » cac he, mac le, bac le
vi va » vi van, vai va, vu va
thiet » thieu

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach le) or (((cach le) OR (cac le)))) van xay hoi. hieu va giai duc van hanh vi va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach le) OR (((cach le) OR (cac le)))) van xay hoi. hieu va giai duc van hanh vi va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach le) or (((cach le) OR (cac le)))) van xay hoi. hieu va giai duc van hanh vi va thiet".
• Adding a wildcard symbol may retrieve word variants: su ((sach le) or (((cach le) OR (cac le)))) van xay hoi. hieu va giai duc van hanh vi va thiet*.