[1] To this period of his life belongs a quarrel with Robortello, due to the publication by Sigonius of a treatise De nominibus Romanorum, in which he corrected several errors in a work of Robertelli on the same subject.

The quarrel was patched up by the intervention of Cardinal Seripando (who purposely stopped on his way to the Council of Trent), but broke out again in 1562, when the two rivals found themselves colleagues at Padua.

[1] In 1583, Sigonius edited a manuscript purported to be the long-sought Consolatio by Cicero, written as a distraction from his grief at the death of his daughter Tullia.

[2][1] Sigonius's reputation chiefly rests upon his publications on Greek and Roman antiquities, which may even now be consulted with advantage: In order to obtain material for these works, Sigonius consulted all the archives and family chronicles of Italy, and the public and private libraries, and the autograph manuscript of his De regno Italiae, containing all the preliminary studies and many documents not used in print, was discovered in the Ambrosian library of Milan.

[1] At the request of Pope Gregory XIII, he undertook a project to write the history of the Christian Church, but did not live to complete the work.