Analysis of information sources in references of the Wikipedia article "Tsar" in English language version.
The Slavonic Bible did equate the terms "tsar" and "king"... Russian writers often compared the grand prince or tsar with any kings of the Old Testament. Several writers [argued] that it was a mistake to translate tsar as "emperor". This was important because of a widely held view in Europe that the tsar wished to claim the imperial legacy of the defunct Byzantine Empire.
The primary meaning of tsar was thus an independent ruler, with no overlord, who could be either a king of one particular nation or people, as in the Bible, or an 'emperor' ruling over several antions, such as the East Roman Emperor.
Other powers [forgot] that tsar had once been recognized as Empereur, as imperator, or even as kayzer... This explains much of the difficulty encountered by Peter I when he adopted the title Imperator. The etymological origin of the word tsar had been glossed over and the title had been devalued.
[...] Michael of Tver', after receiving the yarlyk (edict) of the Mongol Khan in 1304 as grand prince of Vladimir and Moscow sent an embassy to the Emperor Andronicos II in which he described himself as basileus ton Ros.
Ivan III had occasionally, not regularly, used the title 'tsar' in letters to other rulers.
[...] White Tsar [Belyi Tsar']. This title was widely used in Russian communication with Asian or Muslim peoples during the nineteenth century and derived its attraction from its 'Asian' appeal. [...I]n late Tsarist times the expression White Tsar was perceived as a specific 'oriental' title for the Russian Tsar that was rooted in Mongolian traditions.
