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