Perhaps you should try some spelling variations:
khan thong » khap thong, khau thong, nhan thong
sach pham » sach tham, sach phat, sach phap
pham thuc » phap thuc, pham chuc, nham thuc
thuc bach » truc bach, thuc cach, thuoc sach
bach khoa » anh khoa
thuat san » thuat toan, thuat song, thuat lanh
dan thuc » dan toc, am thuc
bach kho » bac ho, benh kho, bach ha
kho khan » khoa kham, khoa than
tu sach » thu sach, su sach, te sach
khoa he » hoa he, khoa hoc, khong he
san dan » sanh dan, shan dan, ban dan

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 pham thuc bach khoa he thong ) or ( thuat san dan thuc bach kho khan thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach pham thuc bach khoa he thong ) OR ( thuat san dan thuc bach kho khan thong )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach pham thuc bach khoa he thong ) or ( thuat san dan thuc bach kho khan thong ))*.