Perhaps you should try some spelling variations:
hien bach » thien hach, hien hanh, dien sach
cac tren » ca tren, cau tren, rac tren
te sach » toc sach
sach ky » sac ky, sach y, sach ty
tuoc va » thuoc va, nuoc va, duoc va
va hanh » van hanh, va thanh, va danh
hanh va » hang va, hanh vi
x hoi » xa hoi, x ho, 5 hoi
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ky nang ((x hoi) or (o hoi)). hieu ((hien bach) OR (vien bach)) tuoc va hanh va cac tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky nang ((x hoi) OR (o hoi)). hieu ((hien bach) OR (vien bach)) tuoc va hanh va cac tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky nang ((x hoi) or (o hoi)). hieu ((hien bach) OR (vien bach)) tuoc va hanh va cac tren".
• Adding a wildcard symbol may retrieve word variants: te sach ky nang ((x hoi) or (o hoi)). hieu ((hien bach) OR (vien bach)) tuoc va hanh va cac tren*.