Perhaps you should try some spelling variations:
"so sanh hanh ky thuat van hoc" » "so xanh hanh ky thuat van hoc", "so danh thanh ky thuat van hoc", "so ban hanh ky thuat van hoc", "so sanh hanh ky thuat san hoc", "so sanh hanh ky thuat va hoc", "so sanh hanh ky thuat ban hoc", "do sanh hanh ky thuat van hoc", "so sanh hanh kem thuat van hoc", "so sanh hanh ky thuat van hoa"
"so sach than ky thuat toan hoc" » "so sach tham ky thuat toan hoc", "so sach han ky thuat toan hoc", "so sach tranh ky thuat toan hoc", "so sach than ky thuat toan khoa", "so sach than ky thuat hoa hoc", "so sach than ky thuat tin hoc", "bo sach than ky thuat toan hoc", "co sach than ky thuat toan hoc", "hoc sach than ky thuat toan hoc"

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (("so sanh hanh ky thuat van hoc") OR ("so sach than ky thuat toan hoc"))~.
• Removing quotes may allow a broader search: (( so sanh hanh ky thuat van hoc ) or ( so sach than ky thuat toan hoc ))~.
• Adding a wildcard symbol may retrieve word variants: (("so sanh hanh ky thuat van hoc") or ("so sach than ky thuat toan hoc"))*.