Perhaps you should try some spelling variations:
sach chuc » cach thuc, sach che, sach thu
toc sach » hoc sach, doc sach, thuoc sach
dan dai » dat dai, dan dat, dan da
cuu tre » cua tre, cau tren, cau treo
va cao » va co, va dao, va bao
luc va » duc va, tuc va, loc va
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: toc sach chuc nang o hoc. hieu ((va cao) or (va cac)) luc va ((dan dai) OR (can dai)) cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach chuc nang o hoc. hieu ((va cao) OR (va cac)) luc va ((dan dai) OR (can dai)) cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach chuc nang o hoc. hieu ((va cao) or (va cac)) luc va ((dan dai) OR (can dai)) cuu tre".
• Adding a wildcard symbol may retrieve word variants: toc sach chuc nang o hoc. hieu ((va cao) or (va cac)) luc va ((dan dai) OR (can dai)) cuu tre*.