Perhaps you should try some spelling variations:
"tu canh tranh nghiem ad hoc" » "tu canh trac nghiem ad hoc", "tu canh trinh nghien ad hoc", "tu canh trai nghiem ad hoc", "tu canh tranh nghiem d hoc", "tu canh tranh nghiem ban hoc", "tu canh tranh nghiem lam hoc", "thu canh tranh nghiem ad hoc", "tu chanh tranh nghiem ad hoc", "tu can tranh nghiem ad hoc"
"tu sach trach nhiem duoc hoc" » "tu sach trac nghiem duoc hoc", "tu sach tranh nhiem duoc hoc", "tu sach truc nhiem duoc hoc", "tu sat trach nhiem duoc hoc", "tu sach trach nghiem duoc hoc", "tu sach trach hiem duoc hoc", "tu sach trach nhiem cuoc hoc", "tu sach trach nhiem quoc hoi", "thu sach trach nhiem duoc hoc", "su sach trach nhiem duoc hoc", "te sach trach nhiem duoc 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 trach nhiem duoc hoc") or ("tu canh tranh nghiem ad hoc"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("tu sach trach nhiem duoc hoc") OR ("tu canh tranh nghiem ad hoc")).
• Removing quotes may allow a broader search: (( tu sach trach nhiem duoc hoc ) or ( tu canh tranh nghiem ad hoc )).
• Adding a wildcard symbol may retrieve word variants: (("tu sach trach nhiem duoc hoc") or ("tu canh tranh nghiem ad hoc"))*.