1. Archives du Musée Teyler, 7, 378: 1933.
2. Making use of Keesom and Kok's results on the discontinuity in the specific heat. Comm. Leiden, 221e; 1932.
3. For example, W. J. de Haas and J. Voogd, Comm. Leiden, 2126c and 214c; 1931. W. J. de Haas Leiziger Vorträge, 59; 1933.
4. Naturwiss., 21, 787; 1933.