Perhaps you should try some spelling variations:
mach khien » mach dien, cach thien
sach tien » sach tren, sach thieu
tien pham » trien pham, tieng phap, thien phat
khien cho » khien hoc, hiem cho, dien cho
khoa hoc » hoa hoc
cho khoa » chi khoa, che khoa, cao khoa
tu sach » thu sach, su sach, te sach
tu mach » tu cach, tu manh, tu hach

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 pham khoa hoc ) or ( tu mach khien cho khoa hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach tien pham khoa hoc ) OR ( tu mach khien cho khoa hoc ))*.