Perhaps you should try some spelling variations:
"toc canh tranh nghien _ hoc" » "toc canh tron nghien _ hoc", "toc canh trong nghien _ hoc", "toc canh truong nghien _ hoc", "luoc canh tranh nghien _ hoc", "ngoc canh tranh nghien _ hoc", "luc canh tranh nghien _ hoc"
"thuoc sach trinh nghien y hoc" » "thuoc sach trinh nghe y hoc", "thuoc sach kinh nghiem y hoc", "thuoc sach trinh thiet y hoc", "hoc sach trinh nghien y hoc", "nuoc sach trinh nghien y hoc", "thuat sach trinh nghien y hoc", "thuoc sach tranh nghien y hoc", "thuoc hanh trinh nghien y hoc", "thuoc sach kinh nghien y hoc", "thuoc sach trinh nghiep y hoc", "thuoc sach trinh nghiem y hoc", "thuoc sach trinh nghien o hoc"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("toc canh tranh nghien _ hoc") or ("thuoc sach trinh nghien y hoc"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("toc canh tranh nghien _ hoc") OR ("thuoc sach trinh nghien y hoc")).
• Removing quotes may allow a broader search: (( toc canh tranh nghien _ hoc ) or ( thuoc sach trinh nghien y hoc )).
• Adding a wildcard symbol may retrieve word variants: (("toc canh tranh nghien _ hoc") or ("thuoc sach trinh nghien y hoc"))*.