Stefanelli, P., C. Carmisciano, F. Caratori Tontini, L. Cocchi, N. Beverini, F. Fidecaro, and D. Embriaco. “Microgravity Vertical Gradient Measurement in the Site of VIRGO Interferometric Antenna (Pisa Plain, Italy)”. Annals of Geophysics, vol. 51, no. 5-6, Dec. 2008, pp. 877-86, doi:10.4401/ag-4459.