Referencing P09

Please acknowledge the use of the DESY photon facility. All publications have to contain a corresponding sentence, which is listed here.

For referencing the beamline P09, please add the additional reference:
[1] J. Strempfer, S. Francoual, D. Reuther, D. K. Shukla, A. Skaugen, H. Schulte-Schrepping, T. Kracht and H. Franz: Journal of Synchrotron Radiation 20, 541-549, (2013). (DOI: 10.1107/S0909049513009011)

For referencing the double phase-retarder, please add the additional reference:
[2] S. Francoual et al., Journal of Physics: Conference Series 425, 132010 (2013)(DOI:10.1088/1742-6596/425/13/132010 )

For referencing the helium-3 fridge, please add the additional reference:
[3] S. Francoual, J. Strempfer, J. Warren, Y. Liu, A. Skaugen, S. Poli, J. Blume, F. Wolff-Fabris, P.-C. Canfield and T. Lograsso, Journal of synchrotron radiation 22(5), 1207 - 1214 (2015)

For referencing the fast switching of circular polarization, please add the additional reference:
[4] J. Strempfer, J. R. L. Mardegan, S. Francoual, L. Veiga, L. Bouchenoire, T Spitzbart and H. Zink, AIP conference proceedings 1741, 030017 (2016) [10.1063/1.4952840]