William Wilson Morgan
3 Jan 1906 – 21 June 1994
William Wilson Morgan (January 3, 1906 – June 21, 1994) was an American astronomer and astrophysicist.[1] The principal theme in Morgan's work was stellar and galaxy classification. He is also known for helping prove the existence of spiral arms in our galaxy. In addition to his scientific achievements he served as professor and astronomy director for the University of Chicago's Yerkes Observatory in Wisconsin and was the managing editor for George Hale's Astrophysical Journal.-Wikipedia
The MK process and stellar classification
A descriptive study of the spectra of the A-type stars
A study of certain characteristics of stellar spectra of type A ..
An atlas of stellar spectra
Revised MK spectral atlas for stars earlier than the sun
Revised MK spectral atlas for stars earlier than the sun