Perhaps you should try some spelling variations:
xin chan » dan chan, ban chan, giu chan
can chan » dan chan, cam chan, ban chan
hieu cac » hieu luc, hieu va, hieu van
co sach » bo sach, cuon sach, hoc sach
so sach » bo sach, hoc sach
so sanh » do sanh
cac hoa » cac hoat, cac khoa, cau hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( co sach ((xin chan) or (can chan)) khoa hoc ) or ( ((so sach) or (so sanh)) hieu cac hoa hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( co sach ((xin chan) OR (can chan)) khoa hoc ) OR ( ((so sach) OR (so sanh)) hieu cac hoa hoc )).
• Adding a wildcard symbol may retrieve word variants: (( co sach ((xin chan) or (can chan)) khoa hoc ) or ( ((so sach) or (so sanh)) hieu cac hoa hoc ))*.