Perhaps you should try some spelling variations:
sach tranh » canh tranh
tranh thuc » trinh thuc, trang thuc, thanh thuy
sach tron » sach tren, sanh trong, sach tien
tron thuc » trong thuc, toan thuc, trong thu
doi thong » doi thuong, doi tuong, doi trong
thuc cac » thuc cach, tuc cac, phuc cac
khoan he » khoa he, khoan ke, khoan le
cac khoa » cac khoi, dac khoa, cao khoa
khoa doi » hoa doi, khoa hoi, khoa noi
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 tranh thuc cac khoan he thong ) or ( tu sach tron thuc cac khoa doi thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach tranh thuc cac khoan he thong ) OR ( tu sach tron thuc cac khoa doi thong )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach tranh thuc cac khoan he thong ) or ( tu sach tron thuc cac khoa doi thong ))*.