Perhaps you should try some spelling variations:
sach thanh » sach tranh, sach tham, danh thanh
thuyet hoa » thuyet va, huyet hoc
toc sach » hoc sach, doc sach, thuoc sach
thanh ky » hanh ky, than ky, thanh tay
thuat do » thuat o
ngan hay » ngan han, ngan hang, nganh xay
ngan ky » nganh ky, nhan ky, nganh ke
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) OR (ngan hay)) thuyet 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) OR (ngan hay)) thuyet 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) OR (ngan hay)) thuyet hoa hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( toc sach thanh ky thuat do hoc ) or ( te sach ((ngan ky) OR (ngan hay)) thuyet hoa hoc ))*.