Perhaps you should try some spelling variations:
thien van » thi van
tinh voi » trinh voi, tinh doi, binh voi
truc may » tren may, truc va
lam truc » lam truoc, nam truc, lam thuoc
tu sach » thu sach, su sach, te sach
voi cua » hoi cua, doi cua, moi cua
hieu ve » hieu va, hieu van
sach ty » sach y, sach tu, sach thu
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
cua tre » cua te, cuu tre, cua triet

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 ty ((nang xa) OR (nang ma)) hoi. ((hieu ve) or (thien van)) lam truc may tinh voi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((nang xa) OR (nang ma)) hoi. ((hieu ve) OR (thien van)) lam truc may tinh voi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty ((nang xa) OR (nang ma)) hoi. ((hieu ve) or (thien van)) lam truc may tinh voi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((nang xa) OR (nang ma)) hoi. ((hieu ve) or (thien van)) lam truc may tinh voi cua tre*.