Pirinsko Delo printed in Bulgaria started to publish a page in Macedonian. After the Tito–Stalin split in 1948, those plans were abandoned. This date also coincided with the first claims of Bulgarian linguists as to the Serbianisation of the Macedonian. Officially Bulgaria continued to support the idea of a Macedonian unification and a Macedonian nation but within the framework of a Balkan Federation and not within Yugoslavia. However, a reversal in the Macedonisation policy was already announced in the secret April plenum of the BCP in 1956 and openly proclaimed in the plenum of 1963. 1958 was the first time that a "serious challenge" to the Macedonian position was launched by Bulgaria. These developments led to violent polemics between Yugoslav and Bulgarian scholars and sometimes reflected on the bilateral relations of the two countries. Macedonian views According to the now-prevalent and official Macedonian view in the books in the Republic of North Macedonia, Macedonian was the first official language of the Slavs, thanks to the St. Cyril and St. Methodius's introduction of Slavic literacy language through the Glagolitic script, that was based on Southern Macedonian dialect from the neighbourhood of Thessaloniki, the home of the two saints. Later on, Macedonia fell under the rule of Bulgarians, and the Byzantines regarded all Slavic Macedonians as Bulgarians. According to a fringe theory, supported in North Macedonia, Tsar Samuil's realm in the Early Middle Ages was allegedly the first Macedonian Slavic state. However, Krste Misirkov, who allegedly set the principles of the Macedonian literary language in the late 19th century, stated: "We speak a Bulgarian language and we believed with Bulgaria is our strong power." During the time of the Ottoman Empire, Serbia, Macedonia, Bulgaria, and Greece were all under Ottoman reign. During the nineteenth century, the primary source of identity was religion. Because Slavs in the geographical regions of Macedonia and Bulgaria were both Orthodox Christian and the Greek Orthodox Church was attempting to Hellenize the population, Macedonian and Bulgarian intellectuals banded together to establish a Slavic literary language in opposition to Greek. Two competing centers of literacy rose at the beginning of the nineteenth century: southwestern Macedonia and northeastern Bulgaria. These centers were different enough at every linguistic level to be competing to become the literary language. When the Bulgarian Exarchate was recognized as a millet on par with the Greek millet (on religious grounds), the designation Bulgarian was still a