Slipher, V. M., V. M. Slipher top Edwin Hubble, July 30, 1940, in response to Hubble's catalog of spectrographic images, 1940-07-30
Slipher states he will supply the images and information that Hubble has asked for but asks for a call to discuss a due date that he can send them by.…
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…