Perhaps you should try some spelling variations:
"tu sach trinh nghiep va hoc" » "tu sach trinh nghien va hoc", "tu sach trinh nghe va hoc", "tu sach trinh ghep va hoc", "tu sach tranh nghiep va hoc", "tu sach kinh nghiep va hoc", "tu sach tren nghiep va hoc", "tu sach trinh nghiep vu hoc", "thu sach trinh nghiep va hoc", "su sach trinh nghiep va hoc", "te sach trinh nghiep va hoc", "tu sach trinh nghiep van hoc"
"tu hanh trinh ky lieu hoc" » "tu canh tranh ky lieu hoc", "tu hanh chinh ky lieu hoc", "tu hanh trinh ky lieu khoa", "tu hanh trinh ky li hoc", "du hanh trinh ky lieu hoc", "lu hanh trinh ky lieu hoc", "thuc hanh trinh ky lieu hoc", "tu hanh trinh ky dieu hoc", "tu hanh trinh ky phieu 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 trinh nghiep va hoc") or ("tu hanh trinh ky lieu hoc"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("tu sach trinh nghiep va hoc") OR ("tu hanh trinh ky lieu hoc")).
• Removing quotes may allow a broader search: (( tu sach trinh nghiep va hoc ) or ( tu hanh trinh ky lieu hoc )).
• Adding a wildcard symbol may retrieve word variants: (("tu sach trinh nghiep va hoc") or ("tu hanh trinh ky lieu hoc"))*.