Some images on the website are used under some Creative Commons licenses.

Author attributions:

https://www.flickr.com/photos/giuseppemilo/
https://www.flickr.com/photos/paulslab/
https://www.flickr.com/photos/thomashawk/
https://www.flickr.com/photos/daniel-wehner/
​​https://www.flickr.com/photos/fensterbme/