Walther, Herbert Laser Physics, Max Planck Institute of Quantum Optics, Max Planck Society;
Walther, H. (2003). Generation of photon number states on demand. Fortschritte der Physik-Progress of Physics, 51(4-5), 521-530. Retrieved from http://www3.interscience.wiley.com/cgi-bin/abstract/104528209/ABSTRACT.