Adding ND means that the IDF formula cannot be uniformly determined. Instead, it is the result of the frequency of all meaningful words in the examined document, as well as the underlying absolute number of documents. However, when analyzing web documents for SEO purposes, the potential results are huge, as all pages indexed by Google (or other search engines) are eligible. Nevertheless, to obtain a specific value, the number of search results of all relevant terms in the document is determined and added. For example, in a highly simplified document that only contains the words “Search Engine Optimization” (17,300,00 search results, December 2017) and “Web Analytics” (2,200,000 search results, December 2017), has a ND value of 19,500,000.