Biagi, P. F., P. Caloi, M. Migani, and M. C. Spadea. “Tilting Variations and Seisruieity That Preceded the Strong Friuli Earthquake of May 6th, 1976”. Annals of Geophysics, vol. 29, no. 3, Nov. 1976, pp. 147-52, doi:10.4401/ag-4798.