Vladimir officially converted the Eastern Slavs to Christianity in 988, and the people had adopted Greek Orthodox liturgical practices. At the end of 11th century, the efforts of St. Theodosius of the Caves in Kiev (Феодосий Киево-Печерский, d. 1074) introduced the so-called Studite Typikon to Russia. This typikon reflected the traditions of the urban monastic community of the famous Studion Monastery in Constantinople. The Studite Typikon predominated throughout the western part of the Byzantine Empire and was accepted throughout the Russian lands. In the end of 14th century, through the work of St. Cyprian, metropolitan of Moscow and Kiev, the Studite liturgical practices were gradually replaced in Russia with the so-called Jerusalem Typicon or the Typicon of St. Sabbas - originally, an adaptation of the Studite liturgy to the customs of Palestinian monasteries. The process of gradual change of typica would continue throughout the 15th century and, because of its slow implementation, met with little resistance - unlike Nikon's reforms, conducted with abruptness and violence. However, in the course of 15th-17th centuries, Russian scribes continued to insert some Studite material into the general shape of Jerusalem Typicon. This explains the differences between the modern version of the Typicon, used by the Russian Orthodox Church, and the pre-Nikonian Russian recension of Jerusalem Typicon, called Oko Tserkovnoe (Rus. "eye of the church"). This pre-Nikonian version, based on the Moscow printed editions of 1610, 1633 and 1641, continues to be used by modern Old Believers.
However, in the course of the polemics against Old Believers, the official Russian Orthodox Church often claimed the discrepancies (which emerged in the texts between the Russian and the Greek churches) as Russian innovations, errors, or arbitrary translations. This charge of "Russian innovation" re-appeared repeatedly in the textbooks and anti-raskol treatises and catecheses, including, for example, those by Dimitri of Rostov. The critical evaluation of the sources and of the essence of Nikonian reforms began only in the 1850s with the groundbreaking work of Nikolai F. Kapterev (1847-1917), continued later by Serge Zenkovsky. Kapterev demonstrated—for the first time to the wider Russian audience—that the rites, rejected and condemned by the Nikonian reforms, were genuine customs of the Orthodox Church which suffered alterations in the Greek usage during the 15th-16th centuries, but remained unchanged in Russia. The pre-Nikonian liturgical practices, including some elements of the Russian typicon, Oko Tserkovnoe, were demonstrated to have preserved many earlier Byzantine material, being actually closer to the earlier Byzantine texts than some later Greek customs (Kapterev, N.F. 1913; Zenkovsky, S.A. 2006).
Remarkably, the scholars who opened the new avenues for re-evaluation of the reform by the Russian Church — Kapterev and E.E. Golubinsky — themselves held membership of the "official" church, but took up study of the causes and background of the reforms and of the resulting schism. Their research revealed the official theory regarding the old Russian books and rites as unsustainable. Zenkovsky has described Kapterev's as [...] the first historian who questioned the theory about the “pervertedness” or incorrectness of the Old Russian ritual and pointed out that the Russian ritual was not at all perverted, but had on the contrary preserved a number of early Old Byzantine rituals, among them the sign of the cross with two fingers, which had been changed later on by the Greeks themselves, in the 12th and 13th century, which caused the discrepancy between the Old Russian and the New Greek church rituals. — Zenkovsky, S.A., Russkoe staroobrjadčestvo, 1970,1990, p. 19-20.