Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh hai » thanh hai, nhanh hai, hang hai
dang van » hoang van, hang va
hai cua » thai cua, dai cua, hoi cua
va hanh » van hanh, va thanh, va danh
cac luc » cau luc, coc luc, cac nuoc
hieu va » lieu va, hieu qua
nang xa » nang x, lang xa, nang ma
luc va » duc va, tuc va, loc va
cua su » qua su

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)) y ((nang xa) or (dang van)) hoi. hieu va cac luc va hanh hai cua su~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) y ((nang xa) OR (dang van)) hoi. hieu va cac luc va hanh hai cua su.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) y ((nang xa) or (dang van)) hoi. hieu va cac luc va hanh hai cua su".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) y ((nang xa) or (dang van)) hoi. hieu va cac luc va hanh hai cua su*.