found:NUCMC data from Columbia Univ. Libraries, Bakhmeteff Archive (New York, N.Y.) for Kiselevskiĭ, G.M. Papers, 1652-1966(Ivan VI, 1740-41)
found:Bolʹsh. sov. ėnt︠s︡., 3rd ed.:v. 9 (Ivan VI Antonovich; 1740-1764; Russian Emperor from 1740-41, grandson of Ivan V; overthrown by Elizaveta Petrovna II on 11-25-1741; subsequently exiled and then imprisioned at Slisselburg Fortress, executed there during attempt by V.I︠A︡. Mirovich to rescue him)
found:Russ. Brockhaus:v. 9, p. 694 (Īoann VI Antonovich, sometimes called Īoann III; proclaimed Emperor Oct. 1740 with his mother as regent; arrested and exiled 12-25-1741)
found:Azbuchny ̆ukazatelʹ imen russ. di︠e︡i︠a︡teleĭ, 1887:p. 316 (Īoann Vasilʹevich, Imperator Vserossīĭskīĭ; b. 08-02-1740, d. 07-04-1764)
found:LC manual auth. cd.(hdg.: Ivan VI, Emperor of Russia, 1740-1764; usage: Ivan IV, Iwan III, Iwan VI)
found:Ivan de Russie, 1841:title page (by Charles LaFont; about Ivan the VI Emperor of Russia)
found:Wikipedia, 24 February 2017(Ivan VI of Russia; Ivan VI Antonovich of Russia (Ioann Antonovich; 23 August [O.S. 12 August] 1740--16 July [O.S. 5 July] 1764) was nominally Emperor of Russia in 1740-1741; he was only two months old when he was proclaimed Emperor and his mother named regent; scarcely a year later his first cousin twice-removed, Elizabeth, seized the throne in a coup, ruling thereafter as Empress of Russia; Ivan and his parents were imprisoned far from the capital and spent the rest of their lives in captivity; after more than twenty years as a prisoner, Ivan was killed by his guards when some army officers (unknown to Ivan) attempted to free him; his surviving siblings, who had been born in prison, then were released into the custody of their aunt, the Queen of Denmark, but none could live normally after a lifetime of confinement; Ivan was born in Saint Petersburg, the eldest child of Duke Anthony Ulrich of Brunswick-Lüneburg by his wife, Duchess Anna Leopoldovna of Mecklenburg-Schwerin, the only niece of the childless Empress Anna of Russia, and the only granddaughter of Tsar Ivan V; he died in Shlisselburg, Russia)
Ivan VI of Russia
Label from public data source Wikidata