Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
dien cuc » dien tu, dieu cua, vien cac
dien cua » dieu cua, dien cu, tien cua
va danh » va dinh, va dan, va hanh
vu nang » vuc nang, va nang, vu dang
hieu va » lieu va, hieu qua
cam tuc » cam xuc, cam tu, nam thuc
tuc va » thuc va, truc va, tuc xa
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 ((dien cua) OR (dien cuc)) 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 ((dien cua) OR (dien cuc)) 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 ((dien cua) OR (dien cuc)) tre".
• Adding a wildcard symbol may retrieve word variants: ((hoc sinh) or (doc sach)) vu nang o hoc. hieu va cam tuc va danh ((dien cua) OR (dien cuc)) tre*.