Perhaps you should try some spelling variations:
sach tranh » canh tranh
mach khien » mach dien, cach thien
khien chua » khien cua, khien qua, khien cho
sach tren » sach tien
chai khoa » thai khoa, chi khoa, pham khoa
chua khoa » khuan khoa, cuu khoa, cu khoa
khoa hoc » hoa hoc
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 tren) or (sach tranh)) chai khoa hoc ) or ( tu mach khien chua khoa hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu ((sach tren) OR (sach tranh)) chai khoa hoc ) OR ( tu mach khien chua khoa hoc )).
• Adding a wildcard symbol may retrieve word variants: (( tu ((sach tren) or (sach tranh)) chai khoa hoc ) or ( tu mach khien chua khoa hoc ))*.