Pirani, Felix A. E (9 de abril de 2009), «Republication of: On the physical significance of the Riemann tensor», General Relativity and Gravitation, 41 (5): 1215–1232, Bibcode:2009GReGr..41.1215P, doi:10.1007/s10714-009-0787-9
Hermann Bondi; F. A. E. Pirani (8 de fevereiro de 1989). «Gravitational Waves in General Relativity. XIII. Caustic Property of Plane Waves». Proc. Roy. Soc. A. 251 (1227). 395 páginas. Bibcode:1989RSPSA.421..395B. doi:10.1098/rspa.1989.0016
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Pirani, Felix A. E (9 de abril de 2009), «Republication of: On the physical significance of the Riemann tensor», General Relativity and Gravitation, 41 (5): 1215–1232, Bibcode:2009GReGr..41.1215P, doi:10.1007/s10714-009-0787-9
Hermann Bondi; F. A. E. Pirani (8 de fevereiro de 1989). «Gravitational Waves in General Relativity. XIII. Caustic Property of Plane Waves». Proc. Roy. Soc. A. 251 (1227). 395 páginas. Bibcode:1989RSPSA.421..395B. doi:10.1098/rspa.1989.0016