One application of federated searching is the metasearch engine. However, the metasearch approach does not overcome the shortcomings of the component search engines, such as incomplete indexes. Documents that are not indexed by search engines create what is known as the deep Web, or invisible Web. Google Scholar is one example of many projects trying to address this, by indexing electronic documents that search engines ignore. And the metasearch approach, like the underlying search engine technology, only works with information sources stored in electronic form.