Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
cau treo » cau theo, cau tren, cau triet
doc sach » hoc sach, nuoc sach, dac sac
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
cao luc » bao luc, cao duc, cao suc
cuu tre » cua tre, cau tren
v nang » va nang, vu nang, van nang
luc va » duc va, tuc va, loc va
va dan » ca dan, va dao, va dau
dan di » danh di, dan da, dan de
va cao » va cac, va co, va dao

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) OR (doc sach)) v nang xa hoi. hieu va cao luc va dan di ((cuu tre) or (cau treo))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) v nang xa hoi. hieu va cao luc va dan di ((cuu tre) OR (cau treo)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) v nang xa hoi. hieu va cao luc va dan di ((cuu tre) or (cau treo))".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (doc sach)) v nang xa hoi. hieu va cao luc va dan di ((cuu tre) or (cau treo))*.