This surplus would allow the replacement of the ox by the horse after the introduction of the padded horse collar in the 12th century.
Islam eventually penetrated into Eastern Europe in the 920s when Volga Bulgaria exploited the decline of Khazar power in the region to adopt Islam from the Baghdad missionaries. The state religion of Khazaria, Judaism, disappeared as a political force with the fall of Khazaria, while Islam of Volga Bulgaria has survived in the region up to the present.
en:William Stahl, Roman Science, (Madison: Univ. of Wisconsin Pr.) 1962, see esp. pp. 120-133.
The proscribed degree of the degree of consanguinity varied, but the custom made marriages annullable by application to the Pope.
