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 nuoc giai thuat hoa hoc" » "so sanh nuoc giai thoai hoa hoc", "so sanh nuoc giai khat hoa hoc", "so sanh nuoc gian thua hoa hoc", "so sach nuoc giai thuat hoa hoc", "so anh quoc giai thuat hoa hoc", "so song nuoc giai thuat hoa hoc", "so sanh nuoc ngoai thuat hoa hoc", "so sanh quoc gia thuat hoa hoc", "so sanh nuoc thai thuat hoa hoc", "so sanh nuoc giai thuat toan hoc", "so sanh nuoc giai thuyet hoa hoc", "so sanh nuoc giai thuat do hoc", "do sanh nuoc giai 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 nuoc giai 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 sanh nuoc giai thuat hoa hoc")).
• Removing quotes may allow a broader search: (( su sach ngonh ky thuat co hoc ) or ( so sanh nuoc giai thuat hoa hoc )).
• Adding a wildcard symbol may retrieve word variants: (("su sach ngonh ky thuat co hoc") or ("so sanh nuoc giai thuat hoa hoc"))*.