Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
cao tuc » dao tuc, cao duc, cao suc
dan dat » dung dat, dong dat, dinh dat
dan dai » dat dai, can dai, dan da
hieu va » lieu va, hieu qua
tuc va » thuc va, truc va, tuc xa
va cao » va cac, va co, va dao
nang o » nang co, nang ho, nang ro
v nang » va nang, vu nang, van nang
cua tu » cua tuc, cua su, cua cu
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: ((toc sach) OR (doc sach)) v nang o hoi. hieu va cao tuc va ((dan dai) or (dan dat)) cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) v nang o hoi. hieu va cao tuc va ((dan dai) OR (dan dat)) cua tu*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) v nang o hoi. hieu va cao tuc va ((dan dai) or (dan dat)) cua tu*".