We all think of Google as the largest search engine -- and that's true, up to a point. But it brings back only web pages and doesn't actually
search the much larger (up to 5 billion) pages of information in various databases (library catalogs, for instance.)
This huge set of internet resources (not available to most search engines) is called "The Invisible Web."
One of the big search hubs is called "RDN." The RDN is a collaboration (metasearch engine) of over seventy educational and research organisations,
including the Natural History Museum and the British Library and is found at:
www.rdn.ac.uk...
It even searches the amusingly named "eevl"
www.eevl.ac.uk... (which is an engineering search engine)