"Gregor von Helmersen"@en . "1803-09-29Z"^^ . . . . . "Gregor von Helmersen (11 October [O.S. 29 September] 1803 \u2013 15 February [O.S. 3 February] 1885) was a Baltic German geologist.He received an engineering training and became major-general in the corps of Mining Engineers."@en . "1885-02-03Z"^^ . "Helmersen, Gregor von"@en . "Estonian geologist" . "1803Z"^^ . . . "1885Z"^^ . . .