（英文）Stewart SA, Allen PJ. A 20-km-diameter multi-ringed impact structure in the North Sea. Nature. 2002, 418 (6897): 520–3. PMID 12152076. doi:10.1038/nature00914.
Monteiro, J. F. The Guarda Circular Structure: A Possible Complex Impact Crater. Abstracts of the Lunar and Planetary Science Conference. 1991, 22: 915. Bibcode:1991LPI....22..915M.
Ormö, Jens; Pio Rossi, Angelo; Komatsu, Goro; The Sirente crater field, Italy.Meteoritics & Planetary Science, 37.11, pp. 1507-1521, 2002; Jens ORMÖ, David GOMEZ-ORTIZ, Patrick C. MCGUIRE, Herbert HENKEL,
Goro KOMATSU, and Angelo Pio ROSSI, Magnetometer survey of the proposed Sirente meteorite crater field, central Italy: Evidence for uplifted crater rims and buried meteorites, Meteoritics & Planetary Science42.2, 211–222, 2007;Ormö, J, Koerbel, C, Rossi, A. P. and Komatsu G; Geological and geochemical data from the proposed Sirente crater field: New age dating and evidence for heating the target, Meteoritics & Planetary Science, Vol. 41, 1331-1435, 2006
（英文）Stewart SA, Allen PJ. A 20-km-diameter multi-ringed impact structure in the North Sea. Nature. 2002, 418 (6897): 520–3. PMID 12152076. doi:10.1038/nature00914.
