“FIMI: Certificazioni Archivio”. FIMI. 2014年8月11日閲覧。 Note: To retrieve the certifications, 1) type in Katy Perry in the box of "Artista", 2) select "--" in the box of "Seleziona settimana e anno", 3) select "Album e Compilation" in the box of "Scegli la sezione" for albums or "Online" for singles, 4) click on "Avvia la Ricerca"
ifpi.at
“Gold & Platin” (To access, user must enter the search parameter "Katy Perry" as Interpret). International Federation of the Phonographic Industry. 2011年4月7日閲覧。
“Gold Platinum Database” (To access certifications, enter either the artist or the title of the item you are looking for into one of the search parameters.). Canadian Recording Industry Association. 2011年9月21日閲覧。
