In addition to the consultation of the stories and gags themselves, as well as the works quoted in the bibliography, the results were crossed with other information available on several sites of Carl Barks or Keno Don Rosa's enthusiasts. This made it possible to dispel some errors of carelessness or to focus on certain stories or gags posing problems.

Internet sites concerned are all referred in the links of this site.

Lastly, another essential source of information was the great number of e-mails exchanged with other ducks' enthusiasts as well as Keno Don Rosa himself (see the page of Acknowledgements of this site).