Pribina was not an independent ruler, but Duke Mojmir of Moravia's lieutenant in Nitra, according to Vlasto. He says that Pribina's attempts to achieve independence led to his exile. The identification of "Nitra" with "Nitrava" is not universally accepted by scholars. Imre Boba and Charles Bowlus are among the scholars who challenged that identification. The Hungarian historian Imre Boba says, the Humanist historian Johannes Aventinus wrongly identified Nitrava (granted along with Brno and Olomouc by Louis the German, according to Aventinus) with Nitra, because Nitrava was in "Hunia or Avaria", to the south of Bavaria. He also says that the Latin term ""locus Nitrava"" could not refer to a city. According to his view, none of the modern names of Nitra (Slovak Nitra, Hungarian Nyitra and German Neutra) could develop from a "Nitrava" form. Boba's linguistic approach is not compliant with onomastic research which suggests that Nitra was the primary form of the place name and "Nitrava" is only the secondary name; both forms were recorded already in the 9th century. The Czech historian Dušan Třeštík, who says that the association of Nitra with Nitrava cannot be challenged, writes that the latter form developed from the name of the Nitra River, which fits well into the system of Indo-European toponyms; other rivers with similar names are not known. Charles Bowlus also rejects the identification of Nitrava with Nitra, because the latter town was only annexed by Moravia during the reign of Svatopluk, years after Pribina's expulsion, according to a letter that Archbishop Theotmar of Salzburg and his suffragans wrote around 900. According to Třeštík, the content of the letter can be explained as a reasonable mistake of its compilators who knew that the territory was in the past a separate realm different from Moravia.