Perhaps you should try some spelling variations:
thanh di » thanh doi, thanh de, thanh do
hieu van » thien van, lieu va, hieu ve
so sach » so sanh, bo sach, co sach
thuc va » thuc vat, thuc dan, thuc day
hieu va » lieu va, hieu qua
y nang » ky nang, ly nang, v nang
tuc va » truc va, tuc xa, duc va
nang o » nang co, nang ho, nang ro
di cua » dai cua, doi cua, de cua
cua te » cua tu
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: so sach y nang o hoi. ((hieu van) OR (hieu va)) cam ((tuc va) or (thuc va)) thanh di cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y nang o hoi. ((hieu van) OR (hieu va)) cam ((tuc va) OR (thuc va)) thanh di cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach y nang o hoi. ((hieu van) OR (hieu va)) cam ((tuc va) or (thuc va)) thanh di cua te".
• Adding a wildcard symbol may retrieve word variants: so sach y nang o hoi. ((hieu van) OR (hieu va)) cam ((tuc va) or (thuc va)) thanh di cua te*.