Emergency numbers
Emergency telephone numbers are adapted from "List of emergency telephone numbers" by Wikipedia contributors (revision 1373696077), licensed under the Creative Commons Attribution-ShareAlike 4.0 licence (creativecommons.org/licenses/by-sa/4.0). The list was reformatted for use in the app. Numbers can change and may be incomplete; check locally.
Country borders
Country borders used to work out which country you are in come from Natural Earth (naturalearthdata.com), 1:10m admin 0 countries, which is in the public domain. They were simplified for use on a phone. Borders shown do not imply any position on disputed territory.
Maps
Map imagery is provided by Apple Maps on iOS and Google Maps on Android, under their own terms.
Open-source software
Petra is built with open-source software, including React Native, Expo, React Navigation, Supabase client libraries, Sentry and PostHog, each under its own licence (mostly MIT or Apache 2.0). [Operator: generate a full list of third-party licences before release, e.g. with npx license-checker --production.]
Fonts
Instrument Sans, by the Instrument team, and IBM Plex Mono, by IBM, both under the SIL Open Font License 1.1 (openfontlicense.org). They are bundled with the app through the Expo Google Fonts packages.
Icons and pictures
The Petra icon, the splash screen and the pictures in the app are made for Petra. Pictures in articles are credited in the article where they are not our own.