%%%%% Tip: Bibtex from DBLP http://dblp.org/ is usually very good.
%%% URLs are only needed for web pages, not for regular articles
@misc{TantauWM11,
  title={The {BEAMER} Class User Guide for version 3.36.},
  author={Till Tantau and Joseph Wright and Verdan Miletić},
  url={http://mirrors.ctan.org/macros/latex/contrib/beamer/doc/beameruserguide.pdf},
  howpublished={[Online; Stand 20. September 2016]},
  year={2011}
}

%% If you really need to cite Wikipedia, then use the "Cite this page" tool:
%% The generated url includes the exact VERSION. Then fix the bibtex...
%% Insert additional curly brackets to prevent parsing of author names etc. 
@misc{dewiki:latex-beamer,
  author = "Wikipedia",
  title = "{Beamer (LaTeX) --- Wikipedia, Die freie Enzyklopädie}",
  year = "2016",
  url = "https://de.wikipedia.org/w/index.php?title=Beamer_(LaTeX)&oldid=151899369",
  note = "[Online; Stand 20. September 2016]"
}
@misc{enwiki:latex-beamer,
  author = "{Wikipedia contributors}",
  title = "Beamer ({LaTeX}) --- {Wikipedia}{,} The Free Encyclopedia",
  year = "2018",
  url = "https://en.wikipedia.org/w/index.php?title=Beamer_(LaTeX)&oldid=834184840",
  note = "[Online; accessed 9-April-2018]"
}

%% In particular with images, you need to give proper credit!
@misc{wiki:catimage,
   author = "Gage Skidmore",
   title = "{File:Grumpy Cat by Gage Skidmore.jpg} --- {Wikimedia Commons}{,} the free media repository",
   year = "2018",
   url = "https://commons.wikimedia.org/w/index.php?title=File:Grumpy_Cat_by_Gage_Skidmore.jpg&oldid=282562480",
   note = "[Online; accessed 26-March-2018]"
}
