kalkulačka. In: Encyclopaedia Beliana [online]. Bratislava: Slovenská akadémia vied, [cit. 2023-06-12]. Dostupné online.
theguardian.com
GIBBS, Samuel. From cameras to keycards, everyday devices killed off by the smartphone. The Guardian (Londýn: Guardian News and Media Limited), 2014-08-04. Dostupné online [cit. 2023-06-12]. ISSN0261-3077.
worldcat.org
GIBBS, Samuel. From cameras to keycards, everyday devices killed off by the smartphone. The Guardian (Londýn: Guardian News and Media Limited), 2014-08-04. Dostupné online [cit. 2023-06-12]. ISSN0261-3077.