Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
ban hanh » ban hang
nam xuc » cam xuc, nam xua, nam thuc
xuc ban » duc ban, cuc ban, quoc ban
doi cua » hoi cua
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.

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) or (toc sach)) ky nang o hoc. hieu van nam xuc ban hanh ((doi cua) OR (dai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky nang o hoc. hieu van nam xuc ban hanh ((doi cua) OR (dai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) ky nang o hoc. hieu van nam xuc ban hanh ((doi cua) OR (dai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ky nang o hoc. hieu van nam xuc ban hanh ((doi cua) OR (dai cua)) tre*.