Author
Eighteenth Century Collections Online
286
Early English Books Online
228
SpringerLink (Online service)
218
United States. National Aeronautics and Space Administration
183
Galilei, Galileo, 1564-1642
140
Moore, Patrick
138
Kepler, Johannes, 1571-1630
101
Ferguson, James, 1710-1776
87
International Astronomical Union
79
Angelo, Joseph
72
ProQuest (Firm)
70
Copernicus, Nicolaus, 1473-1543
69
ProQuest Ebook Subscriptions
65
Culture Class Collection (University of Pennsylvania)
61
Lawrence J. Schoenberg Collection (University of Pennsylvania)
53
Proctor, Richard A. (Richard Anthony), 1837-1888
52
American Astronomical Society
50
Asimov, Isaac, 1920-1992
50
ESTC (Project)
50
Humboldt, Alexander von, 1769-1859
49
Tirion, Wil
49
Ptolemy, active 2nd century
46
Brahe, Tycho, 1546-1601
45
Ridpath, Ian
43
Sagan, Carl, 1934-1996
43
Edward Potts Cheyney Memorial Fund
42
Pasachoff, Jay M.
42
United States Naval Observatory
41
American Institute of Physics
40
Manilius, Marcus
37
Moxon, Joseph, 1627-1691
37
Newcomb, Simon, 1835-1909
37
Astronomical Society of the Pacific
36
e-libro, Corp
34
Bingham, Caleb, 1757-1817
33
Kaufmann, William J.
33
Sacro Bosco, Joannes de, active 1230
33
Bennett, Jeffrey O.
32
Delambre, J. B. J. (Jean Baptiste Joseph), 1749-1822
32
Gingerich, Owen
32
Flammarion, Camille, 1842-1925
31
Greek Culture Class Collection (University of Pennsylvania)
31
Kanopy (Firm)
31
Project Gutenberg
31
Goddard Space Flight Center
30
Leybourn, William, 1626-1716
30
Ronan, Colin A.
30
Tucker, Mary Evelyn
30
Ball, Robert S. (Robert Stawell), 1840-1913
29
Chaisson, Eric
29
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