Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
dien cua » dieu cua, dien cuc, dien cu
cua tre » cua te, cuu tre, cua triet
va danh » va dinh, va dan, dia danh
vu nang » vuc nang, va nang, vu dang
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, ban hanh
cam tuc » cam xuc, cam tu, nam thuc
nang o » nang co, nang ho, nang ro
va cam » va cham, va cac, va cao
o hoc » co hoc, mo hoc, so hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((hoc sinh) or (doc sach)) vu nang o hoc. hieu va cam tuc ((va danh) OR (va hanh)) dien cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((hoc sinh) OR (doc sach)) vu nang o hoc. hieu va cam tuc ((va danh) OR (va hanh)) dien cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((hoc sinh) or (doc sach)) vu nang o hoc. hieu va cam tuc ((va danh) OR (va hanh)) dien cua tre".
• Adding a wildcard symbol may retrieve word variants: ((hoc sinh) or (doc sach)) vu nang o hoc. hieu va cam tuc ((va danh) OR (va hanh)) dien cua tre*.