*W Markowitz (1959), "Variations in the Rotation of the Earth, Results Obtained with the Dual-Rate Moon Camera and Photographic Zenith Tubes", "Astronomical Journal", vol.64 (1959), pp.
* W Markowitz (1959), «Variations in the Rotation of the Earth, Results Obtained with the Dual-Rate Moon Camera and Photograhic Zenith Tubes», "Astronomical Journal", vol.64 (1959), pp.