Optical frequency standard based on cold Ca atoms. - Jürgen Helmcke; Guido Wilpers; Tomas Binnewies; Carsten Degenhardt; Uwe Sterr; Harald Schnatz; Fritz Riehle (IEEE Trans. Instrum. Meas., 2003)

International comparisons of femtosecond laser frequency combs. - Long Sheng Ma; Zhiyi Bi; Albrecht Bartels; Lennart Robertsson; Massimo Zucco; Robert Windeler; Guido Wilpers; Chris Oates; Leo Hollberg; Scott A. Diddams (IEEE Trans. Instrum. Meas., 2005)