Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
duc van » duc va, duc tan, duc manh
ty hang » ly hang, ty xang, thi hang
hanh va » hang va, hanh vi
qua cao » qua cac, qua ca, qua cai
cao duc » dao duc, cao suc, giao duc
va cua » va chua, via cua, ca cua
cua te » cua tu
ca hoi » cau hoi, cua hoi, co hoi

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) or (thuoc sach)) ty hang ((ca hoi) OR (xa hoi)). hieu qua cao duc van hanh va cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thuoc sach)) ty hang ((ca hoi) OR (xa hoi)). hieu qua cao duc van hanh va cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thuoc sach)) ty hang ((ca hoi) OR (xa hoi)). hieu qua cao duc van hanh va cua te".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thuoc sach)) ty hang ((ca hoi) OR (xa hoi)). hieu qua cao duc van hanh va cua te*.