Perhaps you should try some spelling variations:
thanh van » thanh toan, thanh phan, thanh nhan
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
thuc gia » thuc giai, thue gia, thuc dia
cau treo » cau theo, cau tren, cau triet
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
o hoi » co hoi, o hai, o hoa
o hoc » co hoc, mo hoc, so hoc

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 ky nang ((o hoi) OR (o hoc)). hieu van nam thuc gia ((thanh van) or (thanh san)) cau treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoi) OR (o hoc)). hieu van nam thuc gia ((thanh van) OR (thanh san)) cau treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hoi) OR (o hoc)). hieu van nam thuc gia ((thanh van) or (thanh san)) cau treo".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoi) OR (o hoc)). hieu van nam thuc gia ((thanh van) or (thanh san)) cau treo*.