Some 19th-century historiographical works – including Nándor Knauz's Monumenta ecclesiae Strigoniensis – incorrectly referred to him as archbishop of Esztergom. Chronologically, Desiderius is first mentioned by the 14th-century Illuminated Chronicle. According to its narration, "bishop Desiderius" mediated the peace negotiations, when Solomon, King of Hungary and his rebellious cousins, dukes Géza, Ladislaus and Lampert reached an agreement, which was signed in Győr on 20 January 1064. Despite he is styled as bishop by the chronicle, majority of the historians consider he already served as archbishop of Kalocsa by then, as the transfer of bishops from one diocese to another was a forbidden procedure in the 11th century. He is identical with that "archbishop Ders", whose name is mentioned by the founding charter of the Abbey of Százd around 1067. When comes Peter, founder of the monastery requested exemption from the tax payments, both King Solomon and Desiderius approved it. Desiderius is next referred to as archbishop in the founding charter of the Benedictine Abbey of Garamszentbenedek in 1075, alongside Nehemiah, Archbishop of Esztergom. The Illuminated Chronicle refers to him simply archbishop Desiderius, when narrates that King Géza celebrated Christmas at Szekszárd Abbey in 1076. Accordingly, the "King prostrated himself with tears before the Archbishopand the other ecclesiastical personages and prelates. He said that he had sinned because he had possessed himself of the kingdom of a lawfully crowned king ". Based on this chapter, Nándor Knauz considered that Desiderius was a different prelate and he could be only archbishop of Esztergom, as there were no known "archbishops" of Kalocsa, when he wrote his monograph about the history of the Archdiocese of Esztergom. However it is known that Nehemiah held that dignity from around 1075 to at least 1077. Historian László Koszta argued the above-mentioned chapters of the Illuminated Chronicle were written during the reign of Coloman, King of Hungary. Around that time Lawrence functioned as archbishop of Esztergom. Since his episcopate, tensions appear to have emerged between the sees Esztergom and Kalocsa, which affected the contemporary chronicles too. For instance, that rivalry also appeared in the coeval Life of King Stephen of Hungary, compiled by Hartvik, Bishop of Győr, when it derived the title of the superior of Kalocsa from Esztergom, emphasizing its subsidiarity. Lawrence refused to recognize the Archdiocese of Kalocsa as an equal see in the ecclesiastical hierarchy. According to a non-authentic charter of 1093, Desiderius, "bishop" of Kalocsa was involved in a border dispute with Stephen, Bishop of Pécs. In this year, according to the charter, King Ladislaus I, along with prelates of the kingdom, determined the borders between the Archdiocese of Kalocsa and the Diocese of Pécs. The charter also relates that the monarch took into account both the testimony of Desiderius, and the deed of foundation of the bishopric of Pécs. The forgery was compiled, among others, by the usage of an authentic document from 1090. It is presumable that Desiderius still held the dignity during that time.
