Perhaps you should try some spelling variations:
te sach » toc sach
vu dinh » quy dinh
co xuoc » co duoc, co nuoc, co xuong
sach tu » sach thu, cach tu, sach ty
hieu va » lieu va, hieu qua
tu nong » tu dong, tu cong, tu tong
va hoc » van hoc
va hoi » xa hoi, va hoa
vi cua » vai cua, di cua
cua tu » cua tuc, cua su, cua cu
va co » vo co

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: te sach tu nong ((va hoi) OR (va hoc)). hieu va co xuoc ((vu dinh) or (van dich)) vi cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach tu nong ((va hoi) OR (va hoc)). hieu va co xuoc ((vu dinh) OR (van dich)) vi cua tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach tu nong ((va hoi) OR (va hoc)). hieu va co xuoc ((vu dinh) or (van dich)) vi cua tu".
• Adding a wildcard symbol may retrieve word variants: te sach tu nong ((va hoi) OR (va hoc)). hieu va co xuoc ((vu dinh) or (van dich)) vi cua tu*.