Perhaps you should try some spelling variations:
"te sach trinh nghien duoc hoc" » "te sach trinh nghe duoc hoc", "te sach kinh nghiem duoc hoc", "te sach trinh thiet duoc hoc", "te sach trinh nghiem duoc hoc", "te sach trinh nghia duoc hoc", "te sach tranh nghien duoc hoc", "te hanh trinh nghien duoc hoc", "te sach kinh nghien duoc hoc", "te sach trinh nghien quoc hoi", "toc sach trinh nghien duoc hoc"
"te sach thi nghiem de hoc" » "te sach thuc nghiem de hoc", "te sach thi nghiem d hoc", "te sach thi nghiem te hoc", "te sach thi nghiem ve hoc", "te sach thu nghiem de hoc", "te sach tai nghiem de hoc", "te sach thieu nghiem de hoc", "toc sach thi nghiem de hoc", "te sach thi nghiem du hoc", "te sach thi nghiem dien 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: (("te sach thi nghiem de hoc") or ("te sach trinh nghien duoc hoc"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("te sach thi nghiem de hoc") OR ("te sach trinh nghien duoc hoc")).
• Removing quotes may allow a broader search: (( te sach thi nghiem de hoc ) or ( te sach trinh nghien duoc hoc )).
• Adding a wildcard symbol may retrieve word variants: (("te sach thi nghiem de hoc") or ("te sach trinh nghien duoc hoc"))*.