I'm a history student, currently writing a long paper about Treaty of Neuilly and having trouble finding books about it. In our country I could...

When searching on the internet for historical sources, it is important to make sure that you are using the correct search terms.  When using a search engine, you can put your search term in quotations.  For example, you can search for "Treaty of Neuilly."  This will eliminate search results for other treaties from appearing.  When I searched for the treaty in question, I found that it was most commonly called the Treaty of Neuilly-Sur-Seine.  You might have greater success if you try searching for that entire treaty name in quotations.  When deciding what websites to use as sources, look for .gov and .edu websites.  Governments in the United States, the United Kingdom, and other countries have historical pages with useful information.  Websites ending in .edu are typically run by universities, which may also have useful information.  Below you will find three links.  The first one is a British historical website.  The other two are university websites, one which includes the primary source (the treaty itself).