Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
nam duoc » nam thuoc, da duoc, dat duoc
ma hanh » da hanh, na hanh, ban hanh
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
nang o » nang co, nang ho, nang ro
va cua » va chua, via cua, ca cua
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: thu sach y nang o hoi. hieu van nam duoc ((ma hanh) or (va hanh)) va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach y nang o hoi. hieu van nam duoc ((ma hanh) OR (va hanh)) va cua tre.
• Adding a wildcard symbol may retrieve word variants: thu sach y nang o hoi. hieu van nam duoc ((ma hanh) or (va hanh)) va cua tre*.