Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
dien cua » dieu cua, dien cuc, tien cua
doc sach » toc sach, nuoc sach, dac sac
cac duc » cac du, cao duc, cac dac
hieu va » lieu va, hieu qua
va danh » va dinh, va dan, va hanh
dien cu » dien cuc, dien tu, dieu cua
v nang » va nang, vu nang, van nang
nang o » nang co, nang ho, nang ro
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: ((hoc sach) OR (doc sach)) v nang o hoc. hieu va cac duc va danh ((dien cua) OR (dien cu)) tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((hoc sach) or (doc sach)) v nang o hoc. hieu va cac duc va danh ((dien cua) OR (dien cu)) tre~".
• Adding a wildcard symbol may retrieve word variants: ((hoc sach) or (doc sach)) v nang o hoc. hieu va cac duc va danh ((dien cua) OR (dien cu)) tre*.