Perhaps you should try some spelling variations:
"co sach thieu nghiem y hoc" » "co sach thi nghiem y hoc", "co sach thu nghiem y hoc", "co sach thieu nhi y hoc", "co sach thieu nghiep y hoc", "co sach thieu nghiem _ hoc", "co sach thieu nghiem d hoc", "bo sach thieu nghiem y hoc", "cuon sach thieu nghiem y hoc", "hoc sach thieu nghiem y hoc"
"so canh tranh nghe thong hoc" » "so canh trinh nghe thong hoc", "so canh anh nghe thong hoc", "so canh hanh nghe thong hoc", "so canh tranh he thong hoc", "so canh tranh nghe thuong hoc", "so canh tranh nghe tuong hoc", "so canh tranh nghe thong hoa", "so sanh tranh nghe thong hoc", "bo canh tranh nghe thong hoc", "so danh tranh nghe thong hoc"

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

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