Hubble, Edwin, Edwin Hubble to V.M. Slipher, February 23, 1922, and his response to Slipher's Nebulae Questions, 1922-02-23
Hubble describes characteristics of nebulae to Slipher and attempts to answer Slipher's questions. This includes types of nebulae and associated stars…
Slipher, V. M., V. M. Slipher to Edwin Hubble, March 23, 1923, on the Nebulae publication from 1922, 1923-03-23
Slipher describes that he received a letter from Schlesinger about sending an abstract of their report for the previous year's American section of the…