Perhaps you should try some spelling variations:
"so dan than ky thuat ban hoc" » "so dan than ky thuat bai hoc", "so dan than ky thuat bao hoc", "so dan than ky thuat san hoc", "so dan chan ky thuat ban hoc", "so ban than ky thuat ban hoc", "so van than ky thuat ban hoc", "so dan than ky thuat bang hoc", "so dan than ky thuat van hoc", "co dan than ky thuat ban hoc", "so dac than ky thuat ban hoc"
"so sach nhat ky thuat toan hoc" » "so sach nha ky thuat toan hoc", "so sach phat ky thuat toan hoc", "so sach tham ky thuat toan hoc", "so sach nhat ky thuat toan khoa", "so sach nhat ky thuat van hoc", "so sach nhat ky thuat hoa hoc", "so sanh nhat ky thuat toan hoc", "bo sach nhat ky thuat toan hoc", "co sach nhat ky thuat toan hoc"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("so dan than ky thuat ban hoc") or ("so sach nhat ky thuat toan hoc"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("so dan than ky thuat ban hoc") OR ("so sach nhat ky thuat toan hoc")).
• Removing quotes may allow a broader search: (( so dan than ky thuat ban hoc ) or ( so sach nhat ky thuat toan hoc )).
• Adding a wildcard symbol may retrieve word variants: (("so dan than ky thuat ban hoc") or ("so sach nhat ky thuat toan hoc"))*.