^Arthur MacGregor. Naturalists in the Field: Collecting, Recording and Preserving the Natural World from the Fifteenth to the Twenty-First Century (بالإنجليزية). p. 395. ISBN:978-90-04-32384-1. QID:Q99027412.
^Foust, page 26, thinks that the evidence for this is inadequate and that he may have been a Swede, Dane or German who took service in Russia in some other way. He also claims that Lange was the adopted son of Robert Karlovich Areskin, personal physician to Peter the Great, that is, Robert Erskine, sixth son of Sir Charles Erskine, one of the Erskine Baronets of Alva
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