@article{CRPHYS_2004__5_8_845_0,
     author = {U. Sterr and C. Degenhardt and H. Stoehr and Ch. Lisdat and H. Schnatz and J. Helmcke and F. Riehle and G. Wilpers and Ch. Oates and L. Hollberg},
     title = {The optical calcium frequency standards of {PTB} and {NIST}},
     journal = {Comptes Rendus. Physique},
     pages = {845--855},
     publisher = {Elsevier},
     volume = {5},
     number = {8},
     year = {2004},
     doi = {10.1016/j.crhy.2004.08.005},
     language = {en},
}