Perhaps you should try some spelling variations:
khoa thong » hoa thong, thoai thong, pho thong
khoa khoa » hoa khoa, khuan khoa, khoa hoc
cac khoa » cac khoan, dac khoa, cao khoa
sach mai » bach mai, sach bai, sach mau
cac khoi » cac thoi, cac khoan, cach thoi
tu sach » thu sach, su sach, te sach
tren te » tren xe, tren he, tren nen
so sach » so sanh, bo sach, co sach
khoi he » khoa he, khoi de, khong he
mai tu » tai tu

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 te) OR (tien te)) cac khoa khoa thong ) or ( so sach mai tu cac khoi he thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach ((tren te) OR (tien te)) cac khoa khoa thong ) OR ( so sach mai tu cac khoi he thong )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach ((tren te) OR (tien te)) cac khoa khoa thong ) or ( so sach mai tu cac khoi he thong ))".
• Adding a wildcard symbol may retrieve word variants: (( tu sach ((tren te) OR (tien te)) cac khoa khoa thong ) or ( so sach mai tu cac khoi he thong ))*.