Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
hanh dao » lanh dao, thanh dat, thanh dam
ban hanh » ban hang
dao cua » dai cua, day cua, dan cua
duc ban » duc tan, duc van, dua ban
cac duc » cac du, cao duc, cac dac
hieu ve » hieu va, hieu van
mai hoi » mai khoi, dai hoi, lai hoi
tu nano » truc nano
tu nang » tru nang, tu nong, tu lang
ma hoi » xa hoi, ma hoa, me hoi
ve cac » va cac, vien cac
cua tu » cua tuc, cua su, cua cu

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

• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ((tu nang) OR (tu nano)) ((ma hoi) OR (mai hoi)). hieu ve cac duc ban hanh dao cua tu~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ((tu nang) or (tu nano)) ((ma hoi) OR (mai hoi)). hieu ve cac duc ban hanh dao cua tu~".
• Adding a wildcard symbol may retrieve word variants: doc sach ((tu nang) or (tu nano)) ((ma hoi) OR (mai hoi)). hieu ve cac duc ban hanh dao cua tu*.