openstreetmap.png: 
  https://openstreetmap.org/copyright
humanitarian.png:
  https://www.hotosm.org
  https://www.openstreetmap.fr
cyclosm.png:
  https://leafletjs.com
  https://www.cyclosm.org
opnvkarte.png:
  https://memomaps.de/en/homepage/
opentopomap.png:
  http://viewfinderpanoramas.org/
  https://sonny.4lima.de/
  https://opentopomap.org/
  https://creativecommons.org/licenses/by-sa/3.0/
mapboxstreets.png:
  https://www.mapbox.com/about/maps/
mapboxsattelite.png:
  https://www.mapbox.com/about/maps/
alidadesmooth.png:
  https://maplibre.org/
  https://stadiamaps.com/
  https://openmaptiles.org/
alidadesmoothdark.png:
  https://maplibre.org/
  https://stadiamaps.com/
  https://openmaptiles.org/
