- In Ptolemy’s Geography from the 2nd century, there is mention of (and it is also indicated on a map) a place named Serbinon or Serbinum (This place was located under mountains Biblia ore or Biblini montes or Beby m. which are actually Kozara and Grmeč, according to Hungarian scientists).
- In the book Itinerarium Antonini from the 2nd and 3rd centuries, this name is written as Servitium.
- In a map known as Tabula Peutingeriana from the 4th century, this name is written as Seruitio.
- In the book Notitia dignitatum from about 400 AD, this name is written as Servitii.
- In the book Anonymi Ravennatis Cosmographia from the 7th and 8th centuries, this name is written as Serbitium.
All mentioned forms of the name (including Serbinon, Serbinum, Servitium, Seruitio, Servitii, and Serbitium) refer to a single place, which is identified as present-day Gradiška.
The settlement is primarily believed to have been located on the right bank of the river Savus, but there was also a corresponding settlement on the left bank, near today's Stara Gradiška that some modern-day local sources also identify as Servitium.
In Roman times, the Municipium Servicium was an important crossroad between the east and the south of the Balkans, i.e. a port for the Roman river fleet, which speaks for itself about the strategic importance of the settlement at the time.
- History of Gradiška
- Kljajić, Josip (2002). "Stara Gradiška - grad mrtvih "mrtav grad"" [Stara Gradiška - the City of the Dead "Dead City"]. Histria Antiqua (in Croatian). Pula, Croatia. 8: 403–418. ISSN 1331-4270.
- "Stara Gradiška". Jasenovac Memorial Site. Retrieved 2011-10-23.
[...] Stara Gradiška [...] was founded on the ruins of the nearby late Antique village of Servitium [...]
- "Uvreda za porodice logoraških žrtava". Novosti (in Serbian) (557). Retrieved 2011-10-23.
[...] lokalitetu bogate prošlosti, još od vremena antike i nastanka rimskog naselja Servitium na lijevoj obali rijeke Save [...]
- Aleksandar M. Petrovic, Александар М. Петровић, Кратка археографија Срба (Short Archeography of Serbs), Novi Sad, 1994, page 8