To effectively use an index, you must find out what it covers. Many reference books specialize in information about countries of the world. A good topic statement is precise, concise, and grammatically correct. The same database can have two different search engines. Good article indexing is usually available free on the Internet.
Some databases are searchable in the library building only.
Every index works the same. If you can learn to use one well, all the tricks will work in all the other indexes. It is O.K. to use someone else's sentences in your research paper without putting them in quotes, as long as you don't use whole paragraphs. Most web sites are written by authoritative, scholarly people or organizations whose word can be trusted. Every field has its own set of reference books.