Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
thanh di » thanh doi, thanh de, thanh do
va triet » va thiet, va trien, ve triet
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc dan, thuc day
x hoi » xa hoi, o hoi, 5 hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky nang ((x hoi) OR (x ho)). hieu van nam thuc va ((thanh di) or (thanh pho)) va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang ((x hoi) OR (x ho)). hieu van nam thuc va ((thanh di) OR (thanh pho)) va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky nang ((x hoi) OR (x ho)). hieu van nam thuc va ((thanh di) or (thanh pho)) va triet".
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang ((x hoi) OR (x ho)). hieu van nam thuc va ((thanh di) or (thanh pho)) va triet*.