Perhaps you should try some spelling variations:
"su sach ngonh ky thuat co hoc" » "su sach ngan ky thuat co hoc", "su sach nganh ky thuat co hoc", "su danh ngonh ky thuat co hoc", "su canh ngonh ky thuat co hoc", "su sach ngonh ky thuat do hoc", "su sach ngonh ky thuat o hoc", "vu sach ngonh ky thuat co hoc"
"so sach ngon hay thuat hoa hoc" » "so sach ngan hay thuat hoa hoc", "so danh ngon hay thuat hoa hoc", "so canh ngon hay thuat hoa hoc", "so sach ngon phau thuat hoa hoc", "so sach ngon my thuat hoa hoc", "so sach ngon va thuat hoa hoc", "so sach ngon hay thuat toan hoc", "so sach ngon hay thuyet hoa hoc", "so sach ngon hay thuat do hoc", "so sach ngoc hai thuat hoa hoc", "so sach ngoc ha thuat hoa hoc", "so sanh ngon hay thuat hoa hoc", "bo sach ngon hay thuat hoa hoc", "co sach ngon hay thuat hoa hoc"

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("su sach ngonh ky thuat co hoc") or ("so sach ngon hay thuat hoa hoc"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("su sach ngonh ky thuat co hoc") OR ("so sach ngon hay thuat hoa hoc")).
• Removing quotes may allow a broader search: (( su sach ngonh ky thuat co hoc ) or ( so sach ngon hay thuat hoa hoc )).
• Adding a wildcard symbol may retrieve word variants: (("su sach ngonh ky thuat co hoc") or ("so sach ngon hay thuat hoa hoc"))*.