1. Cohen, R.H., Robinson M., Scarfiglieri G., Sheehy R., Comandini V. V., Waller J. and Xenakis S. (2006) The role of scale economies in the cost behaviour of post in Dieke A. and Niederpum A., Regulating Postal Markets: Harmonised Versus Country-specific Approaches, 8th Königswinter Seminar, WIK Proceedings no 11, Bad Honnef.
2. Cuomo M., Nardone T., Rovero A. and Scarfiglieri G. (2013) Electronic substitution and USO scope definition Chapter 13: in Reforming the Postal Sector in the Face of Electronic Competition edited by: Michael A. Crew and Paul R. Kleindorfer, ISBN 9780857935793.
3. Čorejová, T. and Imríšková, E. (2008) Integracjanarynkuusługpocztowych (Convergence at the postal market). EksploatacjaiNiezawodność. Volume 39, Issue 3, 2008, p 74-76 ISSN 1507-2711.
4. Directive 97/67/EC of the European Parliament and of the Council of 15 December 1997 on common rules for the development of the internal market of Community postal services and the improvement of quality of service.
5. Directive 2002/39/EC of the European Parliament and of the Council of 10 June 2002 amending Directive 97/67/EC with regard to the further opening to competition of Community postal services.