Perhaps you should try some spelling variations:
"su sach ngonh ky thuat co hoc" » "su sach ngon ky thuat co hoc", "su sach ngan ky thuat co hoc", "su sach nganh ky thuat co hoc", "su sach ngonh ky thuat do hoc", "su sach ngonh ky thuat o hoc", "so sach ngonh ky thuat co hoc", "vu sach ngonh ky thuat co hoc"
"so sanh ngoc hai thuat hoa hoc" » "so anh ngoc hai thuat hoa hoc", "so thanh ngoc hai thuat hoa hoc", "so van ngoc hai thuat hoa hoc", "so sanh ngoc phau thuat hoa hoc", "so sanh ngoc giai thuat hoa hoc", "so sanh ngoc khoi thuat hoa hoc", "so sanh ngoc hai thuat toan hoc", "so sanh ngoc hai thuyet hoa hoc", "so sanh ngoc hai thuat do hoc", "do sanh ngoc hai 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 sanh ngoc hai thuat hoa hoc"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"su sach ngonh ky thuat co hoc\") OR (\"so sanh ngoc hai thuat hoa hoc\"))".
• Removing quotes may allow a broader search: (( su sach ngonh ky thuat co hoc ) OR ( so sanh ngoc hai thuat hoa hoc )).
• Adding a wildcard symbol may retrieve word variants: (("su sach ngonh ky thuat co hoc") OR ("so sanh ngoc hai thuat hoa hoc"))*.