At the end of the ninth and the beginning of the tenth centuries, the process of territorial, tribal, and political consolidation the peoples of the Middle Volga had been undergoing for more than a century culminated in the emergence of a political entity founded by the descendants of those Bulgar tribes whom Batbay had led out of the Azov steppes during the first quarter of the eighth century A.D. 
Arab travelers who visited the Middle Volga region during the tenth century identified the territory of the Bulgar state as the geographic area between the rivers Cheremshan (on the south), Sviaga (on the west), Kama (on the north) and Sheshma (on the east). Ibn-Fadlan enumerated most of the rivers he and his embassy had to cross during their trip to the khan of the Bulgars in A.D. 922:
"And we left the country of [these people] Bashkirs and crossed the river Dzharamsan [Cheremshan], then the river Uran [Uren], then the river Uram [Urem], then the Bainakh [Maina], then the river Vatyg [Utka], then the river Niiasna [Neiaslovka], and then the river Dzhavshyz [Gausherma]." 
By the eleventh and twelfth centuries, the Bulgar state had augmented its territory: in the east, its borders reached the river Zai, and in the south, they extended to the Samara. The bulk of the population belonged to five tribes: the Bulgars proper, the Suvars (Savan), the Esegel (Askl), the Bersula, and the Barandzhar. Despite the tribal diversity, the basins of the Volga and the Kama seem to have been characterized by an impressive unity of material culture, as testified by the pottery unearthed since the 1960s in the areas along the upper Sura, Moksha, and Vada rivers. 
Yet the very nature of the fabric of the Bulgar state – a tribal and ethnic conglomerate – was a source of grievous complications during the period of consolidation and centralization. The struggle for supremacy was fueled by tribal rivalries, and travelers noted the rebelliousness of some of the tribes, who submitted only reluctantly to Bulgar rule. During the tenth century, the Suvars and the Bulgars had emerged as the most serious contenders for supremacy, and this polarization had led to the emergence of two political centers: Biliar-Bulgar and Suvar. Each represented the nucleus of a political entity sophisticated enough to have its own ruler, court, and coins. Also during the tenth century, Biliar-Bulgar emerged as the center around which the gathering of the Bulgar lands was completed, once the sovereignty of Suvar was liquidated.
Almush (Almas), the son of the Bulgar prince Shilki, became the yltyvar (ruler) of the Bulgar state, and his decision to adopt Islam had a catalytic effect on the process of consolidation and centralization in his lands. In the spring of 921, Abdallah ibn-Bashtu arrived in Baghdad as the envoy of Almush, the ruler of the peoples of the north, to Caliph Ja'far al-Muktadir. He carried three letters conveying Almush's desire to be instructed in the religion of Islam, for which he was requesting assistance.  It was in response to this request that, in the same year, al-Muktadir sent Ibn-Fadlan's embassy to the land of the Bulgars. The result was that, in 922, the people of the Bulgar state joined the Islamic umma (community of believers). (To be accurate, however, it should be noted that this was the year Islam became the official religion of the Bulgar state, and that even before Ibn-Fadlan's arrival, Islam had become the religion of the people who lived along the shores of the Volga and Kama.) Caliph al-Muktadir's embassy met some "5,000 souls – men and women – [who] had already accepted Islam. They are known under the name Barandzhar."  Another visitor to the area at the beginning of the tenth century was the Arab geographer Abu-Ali Ibn-Rusta, who remarked that «most of them adhere to Islam, they have mosques and elementary schools in their villages." 
Almush stood at the head of a social hierarchy comprised of clearly distinguishable groups: tribal heads and lesser princes were subordinated directly to him; these, in turn, controlled the craftsmen and the semifree peasantry.  The yltyvar of the Bulgars seems to have put a great value on ceremony and symbolism to underline his position, and he also seems to have indulged in some of the trappings of power even before the victory of the Russian prince Sviatoslav over the Khazars in 965 ended the Bulgars' vassalage to the Khazar khan.  Ibn-Fadlan recorded some of these trappings: «the princes were seated to his right, and he asked us to sit to his left; his sons were seated in front of him, and he alone sat on a throne covered with Byzantine brocade."  It seems that Almush had become so elevated in his status that the very perception of his relationship to God had been distorted. Ibn-Fadlan was shocked by the audacity of Almush, who allowed a sermon that read: "O, Allah! Preserve the well-being of the Lord yltyvar, the Lord of the Bulgars."  Ibn-Fadlan reprimanded the ruler of the Bulgars and lectured him on some basic dogmas in Islam: "Truly, the Lord is Allah and nobody but He, the Great and the Almighty, can be addressed in this manner from the minbar [pulpit]." 
One of the true measures of the emancipation of the Bulgar state from Khazar vassalage was the ability of its rulers to establish diplomatic ties and conclude treaties with their neighbors, as well as with the rulers of more distant lands. In 984, for instance, the Bulgars signed their first treaty with Kiev. When that treaty was renewed in 1006, it included trade privileges for the Bulgar and Russian merchants. During 1024 and 1025, the Bulgar ruler Ibrahim sent an embassy to Khorasan; its main purpose was to provide for the cities of Sebzevar and Khosrovdzher, assistance in building mosques and other edifices.  The relationship of the Bulgar state with neighboring Russian principalities was neither smooth nor free of tension. In fact, throughout the twelfth and thirteenth centuries, they clashed frequently. The Russian campaigns against the Bulgars unfolded over an entire century, with the most notable ones taking place in 1120, 1160, 1164, 1172, 1183, 1186, and 1220 – at which times Russian armies devastated the right bank of the Volga, destroying the city of Oshel'. The Bulgars, in turn, penetrated the Russian lands in 1201 and 1219, and it was only the imminent Mongol danger in 1223 that brought the hostilities to an end and led to conclusion of a peace treaty. 
Despite tension and frequent clashes, the relationship between the Bulgar state and the Russian principalities was not solely one of hostilities. Trade and commercial ties were as important for the Bulgars as they were for the Russian principalities, and the economic life of the Bulgar state, although disrupted by hostilities, never came to a halt because of them. Agriculture, crafts, cattle breeding, hunting, fishing, and trade represented the backbone of Bulgar economy.
The Volga-Kama region, with its rich black soil, was suitable for agriculture. The two-field system that was used was particularly suitable for the cultivation of virgin lands. The basic implements were the heavy metal plow with a single share (saban), which was effective for the virgin, black-earth soils, and the light wooden plow with two iron shares used for podzol soils. The climate, more than the soil or agricultural technology, determined the types of crops the Bulgars cultivated. Barley, wheat, and millet seem to have been the traditional crops because most travelers noted their presence in the Volga-Kama region. Ibn-Fadlan commented: "They met us carrying bread, meat, and millet... their food consists of millet and horsemeat but they have also wheat and barley in abundance, and every one of them who planted this harvests it for himself. The ruler does not have any right to this, except for the fact that they all pay him every year one sable pelt per household." 
Ibn-Fadlan's comments are informative not only for reconstructing the profile of Bulgar agriculture but also for shedding light on their tax system. Because no taxes were levied on agriculture, the bulk of the revenues seems to have come from taxes on trade – one-tenth of the goods traded by both Bulgar and foreign merchants was relinquished to the treasury. In addition to the annual sable pelt tax, there were taxes on weddings and on booty taken during military campaigns, even if the ruler had not participated in them.
Plentiful harvests enabled Bulgars both to satisfy their own needs and to trade the excess. Russian chronicles mention the fact that, when famine ravaged the land of Suzdal in 1026, the population could survive only because food was brought in from Bulgar ("privezosha zhito i tako ozhishsha").  Fruits were also plentiful in the Bulgar lands, and travelers were impressed by the orchards, walnut groves, and even melons they saw in those northern lands. Abu Hamid al-Garnati, the twelfth-century Arab geographer who traveled twice to Bulgar noted: «They have so many kinds of fruits that it is impossible to find more than this elsewhere. There is an extremely tasty melon that can be preserved during the winter." 
Crafts were highly developed in Bulgar state, where skilled potters, blacksmiths, coppersmiths, carpenters, stonemasons, jewelers, and tanners could be found not only in the towns but also in villages, where they fashioned goods of outstanding quality, indistinguishable from similar items produced in urban centers.  Bulgar craftsmen became experts in processing the hides and the pelts that were plentiful in an economy in which cattle breeding and hunting played a significant role. In fact, they became such experts in processing leather and fashioning such leather goods as boots, coats, belts, and trunks that their fame extended beyond the Urals, and a certain type of leather came to be known as Bulgari.  The Russians who encountered the Bulgars on the battlefields were impressed that they were all wearing boots ("sut' vse v sapozekh"). 
Bulgar potters developed a technology and style of their own, which has made it possible to identify easily the yellow-reddish earthenware found at various archaeological sites. Most of the bowls, pitchers, pots, cauldrons, cups, and saucers these potters fashioned featured a glazed strip and were often decorated with original motifs. 
The gold and silver jewelry produced by Bulgar craftsmen is particularly interesting: Rings often feature a waterfowl motif, as do the silver and copper twisted bracelets, pendants, and bronze mirrors. The fascination with waterfowl was, in fact, a fascination with ducks, for they were the symbol of life in Bulgar mythology. Particularly relevant to this issue is a legend that has endured among Siberian Tatars to this day, and according to which Earth was born when the duck dived to the bottom of the primeval sea and brought up a piece of mud that it placed afloat on the surface of the water. 
Bulgar stonemasons and carpenters acquired recognition at home, as well as in such faraway places as Central Asia or Vladimir-Suzdal, where they were invited to erect palaces, mosques, and public edifices. At home, they probably erected most of the buildings in a typical Bulgar town: the offiicial buildings, mosques, caravanserais (inns), warehouses, workshops, and houses. Wood was the principal building material, although bricks and stone were also used for public edifices and homes of the well-to-do. Some of the stone buildings were even equipped with a system of central heating. Most dwellings, however, were wooden structures that rose well above the ground and had chimneys through which the smoke from their stoves was evacuated.  Objects of household use and tools came from the forges of blacksmiths, who produced everything from knives, stirrups, cauldron chains, and locks to axes, scythes, and sickles. 
Craftsmen in general, and carpenters and stonemasons in particular, were probably in high demand in the Bulgar lands, which were densely populated. Archaeologists have identified approximately 2,000 villages and 150 towns. Of these, by far the largest and most impressive town was probably Biliar, which was located on Malaia Cheremshan, where it occupied more than 7 million square meters. Only half of its territory has been excavated, but some 1,000 wooden and several dozen brick and stone structures have already been revealed. Among the latter are the ruins of the palace, the caravanserai, and several houses. Smaller than Biliar, but no less prominent, were the cities of Bulgar (on the Volga), Oshel (on the Tetiush), and Kashan (on the Kama), each of which occupied an area of 1 million square meters. Al-Garnati noted, "Bulgar is a big city, its walls are made of oak and the houses in it of pine."  Bulgar and the other cities, however, also had many brick and stone structures. Most numerous in the Bulgar state were the small fortress towns – residences of feudal lords that were protected by two or three rows of earthen ramparts and were also surrounded by unfortified villages. 
Trade constituted a most important branch of the Bulgar economy. Bulgar merchants engaged in both domestic and foreign trade, but they monopolized the transit trade, utilizing the advantages of their land, which was richly endowed with a network of navigable rivers and located at a crossroads between
Asia and Northern Europe.  From the Caucasus, Central Asia, and Iran came spices, precious stones, rugs, gold, silver, and other luxury items. The Russian principalities sent furs, weapons, and glass ornaments; and European merchants brought cloth, Frankish sabers, and amber. The Bulgars sold grains, honey, beeswax, felt, leather goods (Bulgari), and furs. Slaves were also an important Bulgar trade commodity; as such, they were subject to the tax levied on all traded goods, thus supplying additional revenue for the treasury of the Bulgar ruler. 
It was the intense trade activity that was responsible for the emergence of fairs and marketplaces throughout the territory of the Bulgar state. Aga-Bazar on the Volga was perhaps the most famous, but there were fairs and markets in the cities and the countryside alike. The economic function of the cities – their emergence as trade centers – had a tangible impact on their physical development: caravanserais, which catered to the needs of the eastern merchants, became fixtures in Bulgar towns. The main function of the caravanserai was that of an inn, but most often it doubled as a combination inn, warehouse, and cultural center that provided merchants with food and shelter, storage facilities for their goods, and mosques where Muslims could perform the ritual prayers required by their religion. Christian merchants lived on the outskirts of towns in segregated colonies probably not too different from the nemetskaia sloboda (foreigners' quarters) of medieval Moscow. Eastern coins were used exclusively in trade transactions until the tenth century, when the Bulgars began minting their own. In addition to coins, pelts seem always to have fulfilled the function of units of exchange rather successfully, as suggested by the etymology of the Tatar word tien (squirrel), which stands for the monetary subdivision of a kopek. 
Islam became the nucleus around which the spiritual life of the Bulgar state developed after the tenth century. The Arabic script that accompanied the adoption of Islam became not only the vehicle for disseminating a new religion but also the key to learning and opening the door to the cultural heritage of the Muslim East. It should be noted, however, that the Bulgar lands were hardly a cultural wasteland at the time of their adoption of Islam. On the contrary, they had a rich written culture based on the Turkic runes of the Orkhon type. Writing had developed and spread largely as a means of coping efficiently with economic (taxes, trade), legal, and political matters. Records were kept on wood and salt plaques until the tenth century when paper was introduced from Khorezm in Central Asia. The only reminder of this practice today is the Tatar proverb "Tuzga yazmagann? soil?me," or in liberal translation:
What is not written on saltWith the adoption of Islam, Arabic script replaced the Bulgar runes, and two styles of calligraphy – Qufi and Thuluth – became particularly popular. The literary Bulgar language that emerged during the twelfth century became the vehicle of communication for the new written culture. The ethnic and cultural kinship enjoyed by the Turkic tribes living on the territory of the Bulgar state, along with the increasing centralization, made possible the emergence of such a language, which rendered the existing dialectal differences less significant even if it could not erase them entirely.
Just to mention is a fault.
The existence of a literary language had a profound effect on education, and in turn, that language was enriched by the fruits of education. The Muslim Bulgars had schools where secular subjects received as much attention as the teaching of the religious dogma. In addition to training future ulama (Islamic scholars) and government bureaucrats, these schools provided at least basic literacy for the majority of the population. 
Many Bulgar scholars of the twelfth and thirteenth centuries gained fame and recognition beyond the shores of the Volga and Kama. Al-Garnati was impressed by the work of historian Yakub ibn-Noman, who wrote a history of the Bulgars in 1112. Ibn-Noman was not unique; Burhaneddin Ibrahim ibn-Yusuf had become famous with his books on rhetoric, medicine, and religious commentaries; and no less prominent were the ulama and scholars such as Hamid ibn-Idris, Ahmed al-Bulghari, Muhammed Sadr ibn-Alaeddin, Hasan ibn-Orner, and Muhammed al-Bulgari. 
Unfortunately, history has preserved the name of just one Bulgar poet of this period: Kul Gali. His poem «Kyssa-i Yusuf» has been of interest to literary historians and linguists alike as an outstanding example of the spiritual legacy of thirteenth-century Bulgar society. 
The legacy of the Bulgars endured and, in the nineteenth century, was so tangible that Russian historian S. M. Solov'ev reflected:
For a long time Asia, Muslim Asia built here a home; a home not for nomadic hordes but for its civilization; for a long time, a commercial and industrial people, the Bulgars had been established here. When the Bulgar was already listening to the Qur'an on the shores of the Volga and the Kama, the Russian Slav had not yet started to build Christian churches on the Oka and had not yet conquered these places in the name of European civilization. [Previous] [Next]
1. A. Kh. Khalikov, Proiskhozhdenie Tatar Povolzh'ia i Pruiral'ia (Kazan, 1978), p. 52. For an account of the very early history of the Bulgar lands also see his Volgo-Kam'e v nachale epokhi rannego zheleza. VIII-VI v.v. do n.e. (Moscow, 1977) and Arkheologiia i etnografiia Tatarstana (Kazan, 1976) and, with V. F. Genning, Rannie Bolgary na Volge: Bolshe Tarkhanskii mogil'nik (Moscow, 1964). For other accounts of the history of the Bulgar state, see A. P. Smirnov, Volzhskie Bolgary (Moscow, 1951) and "Nekotorye spornye voprosy istorii Volzhskikh Bolgar," in Istoriko-arkheologicheskii sbornik k 60-letiiu A. V. Artsikhovskogo (Moscow, 1962), pp. 160 – 74; and A. Zabiri, Kiskacha tarih-i Bolghar (Kazan, 1907).
2. A. P. Kovalevskii, ed., Kniga Akhmeda Ibn-Fadlana i ego puteshestvie na Volgu v 921 – 922 g. Stat'i, perevody i komentarii (Kharkov, 1956), p. 131. There is an earlier edition of Ibn-Fadlan's work: I. Iu. Krachkovskii, ed., Puteshestvie Ibn-Fadlana na Volgu (Moscow and Leningrad, 1939); Kovalevskii also produced a monograph based on Ibn-Fadlan's travelogue: Chuvashi i bulgary po dannym Akhmeda Ibn-Fadlana (Cheboksary, 1954). On the issue of historical topography, see A. Iu. Iakubovskii, "K voprosu ob istoricheskoi topografii Itilia i Bolgar v IX i X vekakh," SA 10 (1948): 255-70.
3. A. Kh. Khalikov, Proiskhozhdenie Tatar, pp. 56 – 57 and 63.
4. M. V. Fekhner, Velikie Bulgary. Kazan'. Sviazhsk (Moscow, 1978), p. 8; B. D. Grekov, "Volzhskie Bolgary v IX – X vekakh," in Istoricheskie zapiski, vol. 14 (Moscow, 1945), pp. 3 – 37; B. D. Grekov and N. F. Kalinin, "Bulgarskoe gosudarstvo do mongol'skogo zavoevaniia," in Materially po istorii Tatarii (Kazan, 1948), pp. 97 – 184.
5. Kovalevskii, Kniga Akhmeda Ibn-Fadlana, pp. 13 and 160.
6. Ibid., p. 138.
7. Dina Valieva, "Bolgar sangate sakhifalarennan," KU 1 (1977): 139; for Ibn Rusta's account, see D. A. Khvol'son, ed., Isvestiia o Khozarakh, Burtashakh, Bolgarakh, Mad'iarakh, Slavianakh i Russakh Abu-Ali Akhmeda Ben Omar Ibn-Dasta, neizvestnogo dosele arabskogo pisatelia nachala X veka, po rukopisi Britanskogo Muzeia v pervyi raz izdal, perevel i ob'iasnil D. A. Khvol'son (St. Petersburg, 1869).
8. ITASSR (Kazan, 1973), p. 18.
9. Fekhner, Velikie Bulgary, p. 9; Kovalevskii, Kniga Akhmeda Ibn-Fadlana, p. 140.
10. Kovalevskii, Kniga Akhmeda Ibn-Fadlana, p. 140.
13. Khalikov, Proiskhozhdenie Tatar, pp. 66 – 67.
14. ITASSR (1973), p. 19.
15. Kovalevskii, Kniga Akhmeda Ibn-Fadlana, pp. 131 and 136.
16. Ibid., pp. 140-41.
17. Fekhner, Velikie Bulgary, p. 9.
18. Anas Khalid, "Abu Khamid el-Garnatyining Bolgarga sayakhate. Sayakhatche ham aning asarlare, KU 6 (1976): 153. Garnati's first trip took place in 1135 and 1136, when he spent a year among the Bulgars; in 1150, he stopped briefly in Bulgar on his way to the lands on the Danube. For an analysis of his trip, as well as a Tatar translation of an excerpt from Garnati's travel notes, see the Anas Khalid article mentioned above, pp. 148 – 58. For other editions of Garnati's travelogue, see O. G. Bolshakov and A. L. Mongait, eds., Puteshestvie Abu Khamida al-Garnati v Vostochnuiu i Tsentral'nuiu Evropu (1131 – 1153) (Moscow, 1971); G. Ferrand, ed., Le Tukfat al-albab de Abu, Hamid al-Andalusia al-Garnats edite d'apres les Mss. 2167, 2168, 2170 de la bibliotheque nationale et le Ms. d'Alger (Paris, 1925).
19. Khalikov, Proiskhozhdenie Tatar, p. 69.
20. A. Battal, "Kazan Tiirkleri," in Turk ili (Istanbul, 1928), p. 616; N. Asim, Turk tarihi (Istanbul, 1898), pp. 157 – 200. The date of N. Asim's book is given according to the Muslim lunar calendar. Its equivalent in the Christian (Gregorian) calendar would be 1898. For synchronic charts of the Muslim and Christian years, see Faik Resit Unat, Hicri tarihleri miladi tarihe gevirme kilavuzu (Ankara, 1959), p. 88.
21. ITASSR (1973), p. 16.
22. Khalikov, Proiskhozhdenie Tater, p. 79.
23. Valieva, "Bolgar sangate sakhifalarennan," p. 140.
24. ITASSR (1973), p. 16.
25. Samples of household objects and tools used by the Bulgars are contained in the collection of more than a hundred iron objects that were discovered in 1971 in the Kuibyshev region of the Tatar republic; see Khalikov, Proiskhozhdenie Tatar, p. 80. On architectural and epigraphic evidence concerning Bulgar history, also see I. Berezin, "Bulgar na Volge. S risunkami Bulgarskikh drevnostei i nadpisei," in Uchenye zapiski Imperatorskogo Kazanskogo Universiteta, vol. 3 (Kazan, 1852), pp. 74 – 160, and I. Kazakov, Pamiatniki Bolgarskogo vremeni v vostochnykh raionakh Tatarii (Moscow, 1978).
26. A. Kh. Khalikov, ITASSR (1973), p. 17. The architecture and the beautiful baths of the city of Bulgar impressed other travelers, such as Ibn Haukil (tenth century), Shehabeddin-abu-Abdullah Yakut-et-Himavi (1184 – 1229), Ismail abu-l-Fida (1273 – 1331), Zekeriya-ibn-Muhammad-el-Kazvini (d. 1283), and ibn Batuta (1304 – 1377). The ruins that stand today on the site of Bulgar reveal vestiges of stone-paved streets, water pipes, and stone buildings of the ninth and tenth centuries. See "Biiyiik Bulgar yehri ve onun tarihi hakkinda," Kazan 7 – 8 (1972): 4 – 5. For the history of Bulgar, see also K. F. Fuks, Kratkaia istoriia goroda Kazani (Kazan, 1817). Born in Germany, Karl Fuks (1776 – 1846), attended the Nassau Academy and Marburg University, from which he graduated in 1798 with a degree in medical sciences. In 1805, he traveled to Russia, where he had been appointed a professor of botany and natural sciences at the newly opened Kazan University. Fuks, who never returned to Germany, died in Kazan at the age of 70. He had married a Russian woman, the poetess A. A. Apekhtina, and throughout their lives they took a deep interest in both the academic life of the university and the ethnography and economic and social life of the region. Students of Tatar culture are especially indebted to Fuks for his studies of Tatar ethnographic history. For more biographic data on Fuks, see M. V. Kazanskii, Putevoditel' po Kazani (Kazan, 1899), pp. 207 – 8.
27. Khalikov, Proiskhozhdenie Tatar, p. 78; ITASSR (1973), p. 18.
28. N. N. Firsov, "Nekotorye cherty iz istorii torgovo-promyshlennoi zhizni Povolzh'ia (s drevneishikh vremen do osmotra etogo kraia imperatritsei Ekaterinoi II-oi)," in Izvestiia Obshchestva Arkheologii, Istorii i Etnografii pri Imperatorskom Kazanskom Universitete, vol. 14 (Kazan, 1897), part 1, p. 481; P. Savel'ev, "O torgovle Volzhskikh Bulgar," in ZMNP (St. Petersburg, 1846), p. 32.
29. Fekhner, Velikie Bulgary, p. 10.
30. ITASSR (1973), p. 17; Khalikov, Proiskhozhdenie Tatar, p. 69; Fekhner, Velikie Bulgary, p. 10.
31. For an excellent account of the written culture of the Bulgars, see Gamir Dauletshin, "Bolgar yazma kul'turasy," KU 3 (1980): 176 – 80; also see Kh. R. Kurbatov, Tatar alfavity ham orfografiyase tarikhi' (Kazan, 1960); and G. V. Iusupov, Vvedenie v bulgaro-tatarskuiu epigrafiku (Moscow and Leningrad, 1960).
32. Ahmet Temir, "Kuzey Tiirk ebediyati," in Turk Dunyast El Kitabs, vol. 1 (An-kara, 1976), pp. 505-6.
33. Nurmokhammat Khisamov, "Adabiyatka tarikhi karash," KU 1 (1981): 184; Mirkassyim Gosmanov, "Yanga sakhifalar ach'ila," KU 10 (1980): 155 – 58. Also see Khisamov's monograph "Kyssa-i Yusuf" Kul' Ali. Analiz istoricheskogo siuzheta i av-torskogo tvorchestva (Moscow, 1979).
34. S. M. Solov'ev, Istoriia Rossii s drevneishikh vremen, vol. 5 – 6 (Moscow, 1959-1965), p. 476.