Before revision: References Terquem and Gerono (1855) Nouvelles Annales de Mathematiques: journal des candidats aux écoles polytechnique et normale 14, 83 Some historical references on the precursor work till Carmichael].
After revision: References Further sources Some historical references on the precursor work up toSee also calculus of finite differences umbral calculusDuring Heaviside's lifetime — Carmichael].