Hubble, Edwin, Edwin Hubble to American Philosophical Society Committee on Grants-in-Aid, May 28, 1937, on Slipher's search for a new planet, 1937-05-28
This is the copy of the letter Hubble sent in for the grant to search for a new planet. He emphasized that it would answer an important, ongoing…
Hubble, Edwin, Edwin Hubble to V. M. Slipher, February 9, 1924, on unclassified nebulae and institutional establishment, 1924-02-09
Hubble sent Slipher a memorandum with the letter to pass on to the Committee on Nebulae at the International Astronomy Union, regarding a proposal for…