Keller, M., Lange, B., Hayasaka, K., Lange, W., & Walther, H. (2004). Continuous generation of single photons with controlled waveform in an ion-trap cavity system. Nature, 431(7012), 1075-1078. Retrieved from http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v431/n7012/abs/nature02961_fs.html.