Perhaps you should try some spelling variations:
"tu sach nganh ki thuat do hoc" » "tu sach ngan ki thuat do hoc", "tu sach tranh ki thuat do hoc", "tu cac nganh ki thuat do hoc", "tu sach nganh ky thuat do hoc", "tu sach nganh ke thuat do hoc", "tu sach nganh vi thuat do hoc", "tu sach nganh ki thuat o hoc", "thu sach nganh ki thuat do hoc", "su sach nganh ki thuat do hoc", "te sach nganh ki thuat do hoc", "tu sach nganh ki thuat co hoc", "tu sach nganh ki thuat do hoa", "tu sach nganh ki thuat du hoc"
"tu sach dao ky thuat do hoc" » "tu sach dao ky thuat o hoc", "tu lanh dao ky thuat do hoc", "thu sach dao ky thuat do hoc", "su sach dao ky thuat do hoc", "te sach dao ky thuat do hoc", "tu sach dao ky thuat co hoc", "tu sach dao ky thuat do hoa", "tu sach dao ky thuat du hoc", "tu sach cao ky thuat do hoc", "tu sach dan ky thuat do hoc", "tu sach do ky thuat do hoc"

Try widening your search to All Fields.

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

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