Perhaps you should try some spelling variations:
mach khien » cach thien
sach tien » sach tren, sach thieu
tien chai » tieng thai, tien khi, trien chi
chai khoa » thai khoa, pham khoa, tai khoa
khoa hoc » hoa hoc
chi khoa » nhi khoa, chua khoa, thai 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 chai khoa hoc ) or ( tu ((mach khien) OR (mach dien)) chi khoa hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach tien chai khoa hoc ) OR ( tu ((mach khien) OR (mach dien)) chi khoa hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach tien chai khoa hoc ) or ( tu ((mach khien) OR (mach dien)) chi khoa hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( tu sach tien chai khoa hoc ) or ( tu ((mach khien) OR (mach dien)) chi khoa hoc ))*.