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unknown - CC BY 4.0
Alexander Gardner - Public Domain
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unknown - Public Domain
Frank Ellwood Esshom - Public Domain
w:Artemisboy - Public Domain
Boston Society of Natural History - Public Domain
Juangris - CC BY-SA 4.0
Public Domain
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unknown - CC BY 4.0
Langley, J. N. (John Newport), 1852-1925
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Alexander Gardner - Public Domain
Payne, Lewis, 1845-1865
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Gurney, John Henry 1819-1890
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Adams, Austin, 1826-1890
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Cover credit: International - Public Domain
Vanderbilt, Harold S. (Harold Stirling), 1884-1970
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unknown - Public Domain
Adams, William T. (William Taylor), 1822-1897
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Tuke, Henry Scott, 1858-1929
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Donner, Anders
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Heine, Wolfgang, 1861-1944
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Frank Ellwood Esshom - Public Domain
Kimball, William H. (William Henry), 1826-1907
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Lugard, F. D. (Frederick Dealtry), Sir, 1858-1945
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Thirlwall, Connop, 1797-1875
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w:Artemisboy - Public Domain
Altman, Robert A.
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Bēssariōn, Cardinal, 1403-1472
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Boston Society of Natural History - Public Domain
Minot, Charles Sedgwick, 1852-1914
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Clarke, Mary Anne Thompson, 1776-1852
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Jenkins, Florence Foster, 1868-1944
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unknown - Public Domain
Hinshelwood, Cyril, Sir, 1897-1967
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Juangris - CC BY-SA 4.0
Olson, Charles, 1910-1970
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Porter, James Madison, 1793-1862
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Lowell, Carey, 1961-
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Williams, Montagu Stephen, 1835-1892
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Public Domain
Richardson, Henry Handel, 1870-1946
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unknown - Public Domain
Warren, Harry
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Shaw, Charlotte Frances Payne-Townshend 1857-1943
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Brewer, J. Hart (John Hart), 1844-1900
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O'Shaughnessy, Arthur William Edgar, 1844-1881
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Marstrander, Carl J. S. (Carl Johan Sverdrup), 1883-
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Gertler, Mark, 1891-1939
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Cooper, Susan Fenimore, 1813-1894