Perhaps you should try some spelling variations:
thien van » thi van
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, lieu va, hieu ve
lam tuc » lam thuoc, lam truoc, luat tuc
luu tre » luu tru, cuu tre, luy tre
y nang » ky nang, ly nang, v nang
tuc va » thuc va, truc va, tuc xa
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va
vi luu » vi lua
o hoc » co hoc, mo hoc, so hoc
o hoi » co hoi, o hai, o hoa

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) OR (o hoc)). ((hieu van) or (thien van)) lam tuc va dan vi luu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach y nang ((o hoi) OR (o hoc)). ((hieu van) OR (thien van)) lam tuc va dan vi luu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach y nang ((o hoi) OR (o hoc)). ((hieu van) or (thien van)) lam tuc va dan vi luu tre".
• Adding a wildcard symbol may retrieve word variants: thu sach y nang ((o hoi) OR (o hoc)). ((hieu van) or (thien van)) lam tuc va dan vi luu tre*.