R. Gunzenhäuser, and E. Haas. utb-studi-e-book UTB GmbH and Barbara Budrich, Stuttgart and Opladen, 3., überarbeitete und aktualisierte Auflage edition, (2015)
V. Jiménez, F. Salmhofer, R. Frosch, H. Zeiner, and W. Haas. IoT 360 (1), volume 169 of Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, page 297-303. (2015)
M. Gierczak, U. Bretschneider, P. Haas, I. Blohm, and J. Leimeister. Crowdfunding in Europe – State of The Art in Theory And Practice; FGF Studies in Small Business and Entrepreneurship, Springer Science + Business Media, Cham, (2015)