Perhaps you should try some spelling variations:
sach thien » sach thieu, sach tien, cach thien
thien giao » thien giap, tien giao, trien giao
giao khoa » bia khoa, lao khoa, go khoa
dien bao » dien ban, dien tao, bien bao
dien mao » dien giao, dien va, dien dan
khoa hoc » hoa hoc
tu mach » tu cach, tu manh, tu hach
te sach » toc sach

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tu mach ((dien bao) OR (dien mao)) khoa hoc ) or ( te sach thien giao khoa hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu mach ((dien bao) OR (dien mao)) khoa hoc ) OR ( te sach thien giao khoa hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu mach ((dien bao) OR (dien mao)) khoa hoc ) or ( te sach thien giao khoa hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( tu mach ((dien bao) OR (dien mao)) khoa hoc ) or ( te sach thien giao khoa hoc ))*.