Perhaps you should try some spelling variations:
sach day » sach dat, sach dau, sach hay
sach dao » lanh dao
van hanh » van thanh, ban hanh, van anh
hieu ve » hieu va, hieu van
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
hanh va » hang va, hanh vi
cua tre » cua te, cuu tre, cua triet
va hoi » xa hoi, va hoc, va hoa
ve cac » va cac, vien cac
va cua » va chua, via cua, ca cua

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 day) OR (sach dao)) nano va hoi. hieu ve cac duc van hanh va cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach day) OR (sach dao)) nano va hoi. hieu ve cac duc van hanh va cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach day) OR (sach dao)) nano va hoi. hieu ve cac duc van hanh va cua tre*.