Perhaps you should try some spelling variations:
sach tranh » canh tranh
kxky thuat » kxy thuat
sach hanh » sach han, sac hanh, cach nhanh
sach danh » sach dao, sach dung, sach kinh
thuat du » thuat dau, thuat do, thuat tu
toan hoc » toan khoa, van hoc, hoa hoc
su sach » so sach, vu sach
du hoc » tu hoc, duoc hoc

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

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