... Multi-threaded search engines . ... Unfortunately, most documents on search engines I saw in the Internet were either lists of hyperlinks without any comments, or discussions about how many documents are in the database of ... (here is the name of a search engine) and what method of counting of the number of documents was used. No words about the efficiency, i.e. how many documents on some subject I can find using this search engine, especially in comparison with the other ones. ...