Henrietta Leavitt's Paper on the
Cepheid Variables in the Small Magellenic Cloud Title: Periods of 25 Variable Stars in the Small
Magellanic Cloud. Authors: Leavitt, H. S. & Pickering, E. C.
Harvard Observatory Circular 173 (March 3, 1912), 1-3. Source -
NASA ADS
Edwin Hubble Paper on Cepheid Variables in M31 and M33