The optical calcium frequency standard. - Fritz Riehle; Harald Schnatz; Burghard Lipphardt; Götz Zinner; Tilmann Trebst; Jürgen Helmcke (IEEE Trans. Instrum. Meas., 1999)

Suppression of spurious phase shifts in an optical frequency standard. - Tilmann Trebst; Tomas Binnewies; Jürgen Helmcke; Fritz Riehle (IEEE Trans. Instrum. Meas., 2001)