Ertel, H., and C. G. Rossby, 1949: A new conservation theorem of hydrodynamics. [ PDF ]

Holl, P., 1970: The completeness of the orthogonal system of the Hough Functions. [ PDF ]

Schubert, W. H., E. Ruprecht, R. Hertenstein, R. Nieto-Ferreira, R. K. Taft, C. M. Rozoff, P. E. Ciesielski, and H.-C. Kuo, 2004: English translations of twenty-one of Ertel's papers on geophysical fluid dynamics. Meteor. Zeit., 13, 527-576.