Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
phat xuc » chat xuc, phat xuat, phap xu
dua tren » dung tren
hieu va » lieu va, hieu qua
va dinh » van dinh, va kinh, va tinh
dinh vi » dinh ve, dinh viet, dinh tri
nang o » nang co, nang ho, nang ro
xuc va » duc va, tuc va, luc va
vi dua » vi du, vi dum, vi lua
o hoc » co hoc, mo hoc, so hoc

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

• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky nang o hoc. hieu va phat xuc va dinh vi dua tren~.
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ky nang o hoc. hieu va phat xuc va dinh vi dua tren*.