The first fragment, preserved in the 13th-century Vat. gr. 2014 manuscript (interposed into descriptions of the Avaro-Persian siege of Constantinople and the Second Arab Siege of Constantinople, as well as hagiographical texts) in the Vatican Library, deals with the 811 campaign of Emperor Nikephoros I (r. 802-811) against the Bulgars, which ended in the disastrous Battle of Pliska. Discovered and published in 1936 by I. Duj?ev, it is also known as the Chronicle of 811, or the Duj?ev Fragment.
The second, which is preserved in the early 11th-century B.N. gr. 1711 manuscript in the Bibliotheque Nationale in Paris along with the chronicle of the so-called "Leo Grammaticus", deals with the reigns of Michael I Rhangabe (r. 811-813) and Leo V the Armenian (r. 813-820) that followed after Nikephoros I. The date of authorship is disputed, but the vividness of the narrative suggests that it was written by a contemporary of the events described.
The two fragments were identified as forming part of the same work by Henri Grégoire based on similarities in style. Although generally an unreliable indicator, this hypothesis has since been commonly accepted. Both fragments provide information not included in the contemporary histories of Theophanes the Confessor and Theophanes Continuatus, and Grégoire hypothesized, again based on style, that the Scriptor Incertus was a continuation of the work of the 6th-century historian John Malalas. The second fragment was known to, and used by, the late 10th-century Pseudo-Symeon Magister, but he does not appear to have used it for the sections of his history before Michael I.
Additional literature is given by Paul Stephenson.