Perhaps you should try some spelling variations:
sach thanh » sach tranh, sach tham, danh thanh
sach ngan » sach ngon, sach nha, sach han
ky thuyet » ly thuyet, li thuyet
toc sach » hoc sach, doc sach, thuoc sach
thanh ky » hanh ky, than ky, thanh tay
thuat do » thuat o
ly huyet » ly thuyet, li thuyet, ly chuyen
do hoc » co hoc, do hoa, du 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 thanh ky thuat do hoc ) or ( te sach ngan ((ky thuyet) OR (ly huyet)) hoa hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( toc sach thanh ky thuat do hoc ) OR ( te sach ngan ((ky thuyet) OR (ly huyet)) hoa hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( toc sach thanh ky thuat do hoc ) or ( te sach ngan ((ky thuyet) OR (ly huyet)) hoa hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( toc sach thanh ky thuat do hoc ) or ( te sach ngan ((ky thuyet) OR (ly huyet)) hoa hoc ))*.