Perhaps you should try some spelling variations:
khoan toan » khoan thanh, khoa than, hoa toan
hoach tri » hoach toi, hoach hoi, hoach thu
sach thu » sach thue, sach thieu, sach tham
thu thuc » thuc thuc, thu thuoc, thue thuc
thuc cac » thuc cach, tuc cac, phuc cac
cac khoa » cac khoi, dac khoa, cao khoa
tri thac » tri thuc, tri tac, tri tham
thac cac » thoai cac, thanh cac, thuc cach
tu sach » thu sach, su sach, te sach
khoa he » hoa he, khoa hoc, khong he

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 thu thuc cac khoa he thong ) or ( thu hoach tri thac cac khoan toan thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach thu thuc cac khoa he thong ) OR ( thu hoach tri thac cac khoan toan thong ))*.