Perhaps you should try some spelling variations:
sach tieng » anh tieng, dich tieng, hanh tieng
sach tien » sach thieu
tien thao » tien thanh, tieng thai, tien giao
thao khoa » thai khoa, toan khoa, pham khoa
sach tren » sach tranh
khoa hoc » hoa hoc
nhi khoa » noi khoa, tai khoa, anh khoa
tu sach » thu sach, su sach, te 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 sach tien thao khoa hoc ) or ( tu ((sach tieng) OR (sach tren)) nhi khoa hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach tien thao khoa hoc ) OR ( tu ((sach tieng) OR (sach tren)) nhi khoa hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach tien thao khoa hoc ) or ( tu ((sach tieng) OR (sach tren)) nhi khoa hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( tu sach tien thao khoa hoc ) or ( tu ((sach tieng) OR (sach tren)) nhi khoa hoc ))*.