Perhaps you should try some spelling variations:
sach nganh » sach ngan, cac nganh, sach danh
sach tranh » canh tranh
kxy thuat » ky thuat, ki thuat, my thuat
toan hoc » toan khoa, van hoc, hoa hoc
tu sach » thu sach, su sach, te sach
y thuat » ky thuat, my thuat, ki thuat
do hoc » do hoa, du hoc, mo hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tu sach nganh y thuat ((do hoc) OR (co hoc)) ) or ( tu sach tranh kxy thuat toan hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach nganh y thuat ((do hoc) OR (co hoc)) ) OR ( tu sach tranh kxy thuat toan hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach nganh y thuat ((do hoc) OR (co hoc)) ) or ( tu sach tranh kxy thuat toan hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( tu sach nganh y thuat ((do hoc) OR (co hoc)) ) or ( tu sach tranh kxy thuat toan hoc ))*.