Wikipedia:Multiple sources

Wikipedia's general notability guideline states that "no fixed number of sources [are] required .... but multiple sources are generally expected" in order to establish notability. The word multiple is purposely left vague in the guideline because "sources vary in quality and depth of coverage".

Although in the strictest sense the word "multiple" means "more than one", and in some cases it may indeed be possible to establish notability with only two references, based on existing Wikipedia community norms, it seems that challenges to notability are successfully rebuffed when there are three good in-depth references in reliable sources that are independent of each other. It is important to note that the quality of any reference can always be challenged. A successful challenge would, of course, reduce the number of "good in-depth references". It's a good idea to check the list of "perennial sources" to see if a source is listed as "deprecated",  "banned", or otherwise found to be unreliable by the Wikipedia community.

When considering the quality of the sources, it is helpful, but not mandatory, if the authors and/or publications of the references are notable and have Wikipedia articles. Of course, if the author is notable for being a prankster, or the publication is notable as a tabloid, this reduces the quality of the reference.

Applicability
While references are always needed for verifiability, references are not always needed to establish notability. Wikipedia has criteria for what is called "presumed notability". Examples of established criteria for presumed notability include: Multiple sources are needed to establish notability in cases for which no presumed notability guideline exists.
 * WP:NMUSIC establishes criteria for presumed notability for "musicians, ensembles, composers, lyricists, albums, singles and songs",
 * WP:POLITICIAN establishes criteria for presumed notability for politicians
 * WP:NCREATIVE establishes criteria for presumed notability for creative professionals
 * WP:NACADEMIC establishes criteria for presumed notability for academics

Multiple sources as it relates to events in the news
Since Wikipedia is not a newspaper, citing even 109 news reports that are all independent of each other but essentially report the same thing would not establish notability for the purposes of Wikipedia. In order to show that a subject covered in many news reports is notable, three independent references from three different time periods, would in general successfully rebut notability challenges. References from three different time periods would go a long way to establish the endurance of the subject being covered.