If you are quoting from a source for which it's unknown by whom or when it was written, you can always cite the website you found the information on. If you, for instance, would like to quote something from the website Sparknotes, do the following:
According to Sparknotes, "Jane Austen was way ahead of her time when writing about women's rights."
Therefor, it's of the utmost importance that you include your sources in your documentatiemap so that you can reference this information when writing your essay. If it helps you, you can compile a list of quotes from your book beforehand with the page numbers included.