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", "vu sach ngonh ky thuat co hoc"
"so sach han hay thuat hoa hoc" » "so sach han phau thuat hoa hoc", "so sach han my thuat hoa hoc", "so sach han va thuat hoa hoc", "so sach han hay thuat toan hoc", "so sach han hay thuyet hoa hoc", "so sach han hay thuat do hoc", "so sach tham hay thuat hoa hoc", "so sach danh hay thuat hoa hoc", "so sach nang hay thuat hoa hoc", "so sanh han hay thuat hoa hoc", "bo sach han hay thuat hoa hoc", "co sach han hay thuat hoa hoc", "so sach hang hay thuat hoa hoc", "so sach han day thuat hoa hoc", "so sach han tay 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 han 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 han hay thuat hoa hoc"))*.
• Removing quotes may allow a broader search: (( su sach ngonh ky thuat co hoc ) or ( so sach han hay thuat hoa hoc ))*.