The Internet is considered Public Domain. Be sure to use the following search combination as you navigate the Internet.
Example: Click on Google.com
Type your topic in the search box and add .edu (for Educational websites) ⇒ Global Warming and .edu
OR Type your topic in the search box and add .gov (for Government websites) ⇒ Global Warming and .gov
OR a combination search ⇒ Global Warming and .edu and .gov
Note that the "File Type" box will allow you choose the file type you prefer ⇒ PDF or Microsoft Excel, or Microsoft Word, or Microsoft PowerPoint, etc.
If you simply prefer to use the main Google.com search box, you could do a combination search as well.
Example: Global Warming and .edu and .gov and .pdf or .Ppt etc, etc.
OR Using Google Scholar type your search terms or keywords in the search box...