7 However, although it might well have been totally blotted out on account of the sorry conditions of the period, the memory of this happy union of the Ruthenians with the Apostolic See was not wholly lost with the passage of time. For example in 1458 Gregory Mammas, patriarch of Constantinople, in this holy city, consecrated a certain Gregory as metropolitan of the Ruthenians, who were then subject to the grand duke of Lithuania; and again, more than one of the successors of this metropolitan strove to restore the bond of unity with the Roman Church, although adverse circumstances did not permit the solemn public promulgation of union.
Source: Orientales Omnes Ecclesias (Vatican.va)