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. 2023 Feb 25;128:103158. doi: 10.1016/j.cose.2023.103158

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© 2023 The Author(s)

Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

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Fig. 2 — Overview of topics and how they were merged. Advertisement: COVID-19 related emails that advertise various types of products to the recipient. News: COVID-19 related emails containing news to the reader on all sorts of topics. Information: COVID-19 related emails with the goal to inform the reader about various business topics/situations/regulations etc. Government: COVID-19 related emails that concern political or governmental affairs. Medical: COVID-19 related emails that are focused on health or healthcare in a broader sense. Other: COVID-19 related emails to which no general topic was found.