The More-Like-This feature uses a sophisticated semantic engine to locate publications based on concepts rather than a keyword (text) search. To search using this engine, enough information to allow the formation of an accurate semantic signature is required. Note the engine is presently restricted to English language documents and queries.
One method of creating a More-Like-This query is to use a pre-existing document. This is why documents in the Library with a reasonable amount of English content have an option to perform such a query. In addition to using a Library document, this page also enables the use of the engine with text gathered from a web page or manually entered text.