You can take advantage of any search engine: Google,, Yandex, Rumbler, etc. Enter the search string part of the passage, and on the screen appears a list of sites, pages which posted the text ofs containing the same words that are found in it. At the top of the list will be located in the references in which these words occur in the same order as in the above passage. Review them, make sure the passage is not used in the text, a quote, and you know the name of the original source and its author, which will be indicated in the header.
A special Google "Books" will allow you to significantly reduce the boundaries of the search. To do this, enter a passage or a part in the "Advanced book search" and click "Search". For convenience, take the passage without punctuation. The system will give you a list of books, the text which contains this passage. They should be examined to find the source with author name and title.
Find text in text you can use well-known services – Antiplagiat, such as Advego Plagiatus. Is a free system that can be installed by visiting the website It allows you to search the Internet a partial or complete copy of the text ofovogo document. The intuitive interface of the system allows a high degree of precision to identify the desired text, even if the passage is not quite accurate and the words are swapped. The system will show not only the percentage of the uniqueness of this passage, but give a link to the document part of the content which is most relevant to him. Follow this link and you will be able to see the full desired text.