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