Physical Review Letters, 111-2, 2013 doi:10.1103/PhysRevLett.111.027403
Johannsen Jens Christian, Ulstrup Søren, Cilento Federico, Crepaldi Alberto, Zacchigna Michele, Cacho Cephise, Turcu I. C. Edmond, Springate Emma, Fromm Felix, Raidel Christian, Seyller Thomas, Parmigiani Fulvio, Grioni Marco, Hofmann Philip