The optical calcium frequency standards of PTB and NIST

U. Sterr; C. Degenhardt; H. Stoehr; Ch. Lisdat; H. Schnatz; J. Helmcke; F. Riehle; G. Wilpers; Ch. Oates; L. Hollberg

Comptes Rendus. Physique, Volume 5 (2004) p. 845-855