1. Afuah A, Tucci C (2000) Internet business models and strategies: Text and case. McGraw-Hill Higher Education, New York
2. Alt R, Zbornik S (2002) Integrierte Geschäftsabwicklung mit Electronic Bill Presentment and Payment. In: Weinhardt C, Holtmann C (eds) E-Commerce: Netze, Märkte, Technologien, Proceedings zur Teilkonferenz der Multikonferenz Wirtschaftsinformatik 2002. Physica, Heidelberg
3. Amit R, Zott C (2000) Value drivers of e-commerce business models. INSEAD Working Paper. Fontainebleau, France
4. Anderson C (2009) Free: The Future of a Radical Price. Hyperion, New York
5. Baatz E (1996) Will your business model float?. WebMaster Magazine 10