Nederlands verderop. ENGLISH The worldwide introduction of Bluetooth-based Corona-apps was heavily influenced by research conducted by the research group of professor Christophe Fraser (Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, UK). In particular a paper, "Quantifying SARS-CoV-2 transmission suggests epidemic control with digital contact tracing" written by Luca Ferretti et al., published in Science (and medrxiv.org) describes the simulation model and outcomes used in later advice to the NHS/NHSx and has influenced most later Bluetooth-based Corona-apps. Remarkable difference However, I noticed something fishy. A preliminary version of Ferretti's paper was published by Science on 31 Mar 2020, while the final version was published on 08 May 2020. These versions are mostly identical, except for two things: 1) Minor corrections with irrelevant impact on the simulation results. For example, the preliminary version mentions "The App we propose ..." while ...